Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The multimode memory effect of cholesteric liquid crystals (CLCs) photonic patterns has promising applications for the development of optical sensors, responsive colour decors, and camouflaging techniques. The present memory pattern is mainly aroused from the elastic effect of the polymer network or bistability of the CLC, it is desired for the development of alternative memory mode in non-polymerizable system, which may be helpful for the recyclable use of LC materials for the expired pattern. There remains a challenge for designing photonic patterns with multimode memory effects in a non-polymerized system owing to the limited availability of responsive materials. Herein, photo/heat/electricity/pressure multimode photonic memory pattern was firstly fabricated from non-polymerized cholesteric LC by mixing host LC E7, axially chiral azobenzene-based molecules (ACAMP), and S-form chiral dopants (S5011) based on the combination of PVA alignment layer and photoisomerization of ACAMP. The formed photonic patterns can be reversibly hidden/reappear by controlling the ambient temperature above/below the isotropic temperature or applying combined stimuli of electricity/pressure. The multi-memory pattern from the non-polymerizable system is friendly-environmental (recyclable use) with the simultaneous colour-change of the pattern and background under external stimulus. This study provides new insights into the development of multiresponsive nanostructures with tailorable functionalities, thus presenting new applications in diverse fields ranging from display technologies to information communication.

DOI： 10.1016/j.cej.2022.141215

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We developed optically switchable smart windows driven by sunlight with polymer/liquid crystal (LC) composites containing azobenzene derivatives, which undergo trans-cis isomerization with high efficiency under sunlight. The composites exhibited high transparency in the initial state owing to homeotropic alignment of LCs, which was stabilized by polymer networks. Optical switching from the tranparent state to a light-scattering state was induced isothermally upon exposure to sunlight due to smectic A (SmA) to chiral nematic (N*) phase transition of LCs, triggered by trans-cis photoisomerization of the azobenzenes. The initial transparent state was restored in the absence of sunlight, resulting from N* to SmA phase transition induced by thermal cis-trans back isomerization of the azobenzenes. These autonomic smart windows utilizing only sunlight can be ubiquitously installed without additional artificial sources of energy.

DOI： 10.1039/d2tc02754b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Colorful blue phase liquid crystal (BPLC) patterns have attracted wide research attention owing to their intriguing and advantageous properties and promising applications. However, it remains a challenge to develop novel and high-resolution patterns from BPLC owing to the complicated synthetic procedure for the functional molecules. This study reports a high-resolution "live" pattern by well-designed diffusion of 5CB ink on the wettability-modified BPLC networks. Interestingly, the shape and color of the as-prepared pattern change with time, which results in unique spectra change of the printed pattern, "first red-shift and subsequent blue-shift of the stopband position" and "continuous growth in reflectivity intensity" with time. The hydrophobic substrate greatly suppresses the random spreading and diffusion of ink, contributing to high-resolution patterns. The promising applications of live patterns for program display and active labels are demonstrated. Various high-resolution erasable colorful patterns are obtained. The structure reconfiguration of the writing and erasing processes is proved by transmitted electronic microscope images and Kossel diffraction diagrams, which ensures the reversible writing/erasing of the pattern on the membrane. This work is of significance for the development of novel rewritable paper and high-quality optic devices based on BPLC materials.

DOI： 10.1002/adfm.202110985

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Soft organic lasers with multiwavelength output and high spectral purity are of crucial importance for versatile photonic devices, owing to their monochromaticity, coherence, and high intensity. However, there remain challenges for the achievement of surface-emitting multiwavelength lasing in soft photonic crystals, and the relative mechanisms need to be investigated. Herein, single-, dual-, triple-, and quadruple-wavelength lasers are successfully achieved in dye-doped blue-phase liquid crystal (BPLC) film. The number and wavelength of the lasing peaks can be manipulated by tuning the center of the bandgap, the order parameter of the laser dye, the quality of the resonance cavity, and even the pump energy. For single-wavelength lasing, a lasing peak with an ultranarrow linewidth of 0.04 nm (Q-factor of 13 454) is achieved. Multiwavelength lasing is attained based on the following aspects: i) the narrow bandgaps of the BPLCs with full width at half maximum of 14-20 nm; ii) a laser dye with high gain over a wide wavelength band, having a low-order parameter in the liquid crystal matrix; iii) appropriate relative positions between the reflection and fluorescence peaks; and iv) the highly ordered crystal lattice of BPLC film. The proposed single-to-quadruple-wavelength surface-emitting lasers can be employed as coherent light sources for next-generation optical devices.

DOI： 10.1002/adma.202108330

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Azobenzene actuators have aroused enormous research interest due to their excellent performance and promising applications in the fields of soft robots, artificial muscles, etc. However, there are still challenges for the fabrication of azobenzene actuators with a sophisticated actuation mode owing to the unitary actuation direction and slow thermal relaxation of cis-to trans-azobenzene mesogens. To solve these problems, this paper presents a facile fabrication method of a Janus azobenzene inverse opal actuator with one side made of the monodomain azobenzene polymer and the other side made of the polydomain azobenzene inverse opal structure. Gradient-layer spacing structure of the film in its cross section is proven by synchrotron small-angle X-ray diffraction. The introduction of the inverse opal structure mainly provides a polydomain mesogen alignment, large specific surface area, low elastic modulus, and structure color. The synergetic actuation of the photochemical/photothermal mode produces multiple actuation directions, a larger actuation force, and an alteration of the structure color. Shape self-recovery of this Janus azobenzene actuator contributes to some promising applications, such as crawling on a smooth surface, driving an engine axis, and logic electric circuit for the coding technique. This work is of great significance for the design and fabrication of novel-type photoactuators.

DOI： 10.1021/acsami.1c19826

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Thermoplastic polyurethane containing azobenzene moieties in main chains was developed for photomobile materials capable of reversible photoactuation and shape programming, and was characterized for phase transition properties, microstructures, and photoinduced deformation behaviors. Photomobile films with glassy nature could be fabricated using both melt- and solution-processing methods, in contrast with conventional photomobile materials consisting of chemically cross-linked networks. The alignment of azobenzene moieties and macroscopic shapes in the initial states were controlled by external force under heating above glass transition temperature, which were stabilized by the formation of physical cross-links through hydrogen bonding interactions. The films with uniaxial alignment of azobenzene moieties showed reversible bending upon irradiation with UV and visible light, which could be repeated for 100 cycles. Physical cross-links in the present system can be an alternative for covalent cross-links in photomobile polymer materials, expanding the variety of designs with superior processability.

DOI： 10.1021/acs.macromol.1c01827

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Azobenzene actuator has attracted wide research attention in the fields of soft robots, artificial muscles, etc., owing to the typical photoresponsive material based on its reversible trans-cis isomerization. However, it remains challenging to enhance the actuation performance of azobenzene actuators through simple methods and can work in complex and variable environments. In contrast to complex molecular functional design, this study presents a Janus azobenzene inverse opal actuator: one side of a monodomain azobenzene polymer and the other side of a polydomain azobenzene inverse opal structure. The proposed design can significantly enhance the photoactuation performance in the liquid phase based on the synergetic effects of the Janus structure and the plastic influence of solvent/thermal/photo responses on the polymer segment. Promising applications of photo-driven ring rolling in the liquid phase are demonstrated. The results of this study are of great significance for the design and fabrication of novel-type azobenzene actuators in the liquid phase.

DOI： 10.1002/adfm.202105728

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PORTFOLIO  

In a narrow temperature window in going from the isotropic to highly chiral orders, cholesteric liquid crystals exhibit so-called blue phases, consisting of different morphologies of long, space-filling double twisted cylinders. Those of cubic spatial symmetry have attracted considerable attention in recent years as templates for soft photonic materials. The latter often requires the creation of monodomains of predefined orientation and size, but their engineering is complicated by a lack of comprehensive understanding of how blue phases nucleate and transform into each other at a submicrometer length scale. In this work, we accomplish this by intercepting nucleation processes at intermediate stages with fast cross-linking of a stabilizing polymer matrix. We reveal using transmission electron microscopy, synchrotron small-angle X-ray diffraction, and angle-resolved microspectroscopy that the grid of double-twisted cylinders undergoes highly coordinated, diffusionless transformations. In light of our findings, the implementation of several applications is discussed, such as temperature-switchable QR codes, micro-area lasing, and fabrication of blue phase liquid crystals with large domain sizes. The arrangements of defect lines in liquid crystal blue phases provide promising templates for photonic crystals. Here Liu et al. investigate in detail how inter-phase transitions proceed, by intercepting nucleation with on-demand cross linking of a supporting polymer matrix.

DOI： 10.1038/s41467-021-23631-w

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Molecular alignment in liquid-crystalline elastomers with polysiloxane backbone is controlled with the aid of photoalignment and exchangeable links to enhance performance as photoactuators. The photoalignment is triggered by trans-cis-trans isomerization of azobenzene moieties, which are introduced at crosslinking points, upon irradiation with linearly polarized UV (LPUV) light under heating. The induced alignment is memorized by rearrangement of network structures through exchange reactions of covalent bonds. When irradiated with LPUV light, freestanding films show bending along with the alignment change in surface regions. Macroscopic shapes are also rememorized by exchange reactions at crosslinks. Combination of photoalignment and network rearrangement allows continuous deformation of freestanding films upon exposure to LPUV light with varying polarization directions. This approach enhances the degree of freedom in alignment control, photoactuation, and reshaping of polysiloxane-based liquid-crystalline elastomers, which are feasible as soft actuators.

DOI： 10.1002/adom.202100053

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Rewritable paper, as an environment-friendly approach of information transmission, has potential possibility to conserve energy and promote a sustainable development of our society. Recently, photonic crystals (PCs) have become a research hotspot in the development of rewritable paper. However, there are still many shortcomings that limit the further application of PC paper, such as slow response sensitivity, short-cycle lifetime, poor storage stability, and so on. Herein, we constructed an optically rewritable azobenzene inverse opals (AZOIOs) with a thin film (ca. 1 mu m) plated on an inverse opal structure based on the UV/vis switchable structure color of the sample. The top thin film acts as a protective layer to avoid the large deformation of the pore structure and the bottom inverse opal structure with refractive index/pore structure change that provides reversible structure color. Large, reversible, and rapid bandgap shift (ca. 60 nm, 2 s) of AZOIOs can be repeated more than 100 times under alternating UV/vis irradiation based on isomerization of high content of the azobenzene group. On-demand long-time preservation pattern can be obtained by the appearance of azobenzene's intrinsic color. The proof of concept for rewritable PC paper is demonstrated herein. Such inkless rewritable colorful paper paves a way for developing novel display technology.

DOI： 10.1021/acsami.0c22668

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Photonic shape memory (SM) polymers based on liquid crystalline blue phase (BP) films have been fabricated by self-assembly and subsequent photo polymerization of liquid-crystal mixtures. These freestanding BP films exhibit narrow photonic band gaps and high reflectivity in the visible wavelength range. Multiple blue-shift colors are achieved by SM programming process at different mechanical pressures. The blue-shift colors can be attributed to a decrease of effective BP pitch along the viewing direction caused by the compressed deformation of the BP films, which are confirmed by a three-dimensional interometric profile. The deformed BP films can recover to their original shapes and reflecting colors by heating the polymer films to temperatures above the glass-transition temperature. Quantitative relationships between the shape change and optical response are established for understanding this SM effect. What is more, the temporary photonic patterns can be reversibly written and erased for dozens of cycles without apparent degradation, making these freestanding BP films appealing as rewritable photonic papers and optical sensors.

DOI： 10.1021/acsami.9b14202

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Language：English   Publishing type：Part of collection (book)   Publisher：wiley  

Cross-linked liquid-crystalline polymers (CLCPs) are a representative class of polymer materials showing photomechanical effects. Various 3D motions, such as bending, twisting, and rotation, have been demonstrated since the development of photomobile polymer materials. With the adequate design of CLCPs, the photoresponsive and mechanical properties of these materials have been significantly enhanced. In these systems, 3D motions can be programed through the control of initial molecular alignment. Furthermore, advances in fabrication processes allow flexible design of soft actuators with demanded architectures. In this chapter, structural variation of photomobile polymer materials is overviewed, providing the relationship among structures, mechanical properties, and photoresponsive properties.

DOI： 10.1002/9783527822201.ch8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Fabrication of liquid-crystalline polymer networks with periodic nanoscale features is highly desired for photonic applications. Here, a printable photonic polymer coating has been fabricated from a monodomain liquid crystalline blue phase (BP) network. The BP polymer coating with high reflectivity is covalently linked to the glass substrate, which can be patterned by using an LC-ink to swell the network. The degree of swelling depends on the printed amount of LC-ink which can be controlled through adjusting the voltages of the inkjet printer. Arbitrary multicolour patterns covering the visible spectrum from 451 to 618 nm can be printed and erased multiple times, making these BP polymer coatings promising as rewritable photonic papers and responsive photonic materials.

DOI： 10.1039/c9tc05052c

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

Liquid-crystalline polymers with photodeformable properties have been extensively studied due to their ability of wireless conversion of light energy into mechanical work. With the development of crosslinked liquid-crystalline polymers, various 3D motions, such as bending, twisting, oscillation, rotation, and translational motion have been successfully induced. Recent trends for developing soft robots and microrobots accelerate the progress of photomobile polymer materials. This review is focused on recent advances in the field of photomobile materials based on liquid-crystalline polymers. The structure-function relationship in photomobile polymer materials is overviewed, and the progress in recent years is detailed in terms of complex 3D deformation, continuous motions, self-regulation, and processability.

DOI： 10.1002/adom.201900380

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Here, a facile method is put forward to fabricate freestanding, large-domain blue phase (BP) films based on self-assembly technology. This fabrication method enables the formation of BP domains with large-scale lateral dimensions of similar to 230 mu m, which exhibit sharp photonic bandgaps with high reflectivity. In addition, the large-domain BP structures with good optical performances can be preserved after photopolymerization. What is more, the long-range periodic nanostructures of double-twist cylinders can be directly visualized through transmission electron microscopy, providing a powerful tool to investigate BP structures at the nanoscale. Furthermore, dual-wavelength lasing is achieved by doping the large-domain BP films with fluorescent dyes, which is firstly observed in BP materials.

DOI： 10.1039/c9tc02938a

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Language：English   Publisher：ROYAL SOC CHEMISTRY  

Liquid crystal elastomers, serving as a new kind of intelligent material, have demonstrated important application in the fields of microactuators, artificial muscles, microfluid transportation and intelligent sensors by virtue of their characteristics of spontaneous reversible deformation under external field stimulation. In this paper, we have reviewed the recent research progress of liquid crystal actuator materials, including of phototropic, thermotropic, photothermal and solvent/humidity-based liquid crystal actuators. The processing techniques, deformation response and actuation mechanism of liquid crystal elastomers were discussed and the relative application prospects were put forward. This work will provide important insights for the construction and development of novel liquid crystal optical devices.

DOI： 10.1039/c9tc00107g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Orientation control of ordered materials would not only produce new physical phenomenon but also facilitate the development of fancy devices. Discotic liquid crystals (DLCs) form 1D charge transport pathway by self-organizing into columnar nanostructures via pi-pi stacking. However, controlling the electrical properties in such nanostructures with some direct and instant way is a formidable task for their high viscosity and insensitivity to external stimuli. Herein, the arbitrary control over electrical conductivity of such columnar nanostructures is achieved with UV light by incorporating DLCs with molecular motors. Highly ordered DLC microstripe arrays are generated on desired substrate through a capillary bridge dewetting strategy. The conductivity of the microstripes could be continuously modulated by 365 nm light due to the influence of molecular motion under UV irradiation on the electron orbital overlap of columnar nanostructures. This is so because the disorder degree of the DLC molecules is associated with the intensity of UV light and the doping concentration of molecular motors. Moreover, the device shows memory effect and reversible conductivity change. The DLC microstripe arrays are very promising for the applications in UV detectors, memory devices, optical switches, and so on.

DOI： 10.1002/adma.201806016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The preparation of regular microstructures with liquid crystalline materials for organic field effect transistors (OFETs) is an attractive but challenging issue. However, it is usually limited by the difficulty of forming large-area single crystals aligned in a desirable direction. Herein, several terthiophene (TTP) smectic liquid crystals such as 8-TTP-8 and 12-TTP-11OH are patterned into highly crystalline microstripes by a sandwich system through a dewetting method. Morphology and orientation of the microstripes strongly depend on preparation temperature. Microstripes prepared below crystalline temperature are uniform, well-ordered, and show high field effect transistor (FET) mobility. Meanwhile, pi-pi stacking direction of the TTP backbone is perpendicular to the microstripe and the molecules stack in layer structure, standing up on the SiO2/Si substrate, which would provide an effective pathway for p-type charge transport. However, higher preparation temperatures at liquid crystalline or isotropic liquid range induce many defects in the crystal formation process and cause incline of the unit cell, thus leading to a sharp decrease in FET mobility. A possible mechanism of molecular stacking at different temperature range is proposed. This strategy promised to provide a new opportunity for the high cost-efficiency fabrication of OFETs.

DOI： 10.1002/adfm.201804838

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Composite systems of liquid crystals (LCs) and polymers have been extensively studied in various forms such as polymer-dispersed LCs and polymer-stabilised LCs. Blending LCs and polymers is an effective approach to design functional materials with stimuli responsiveness and durability. Here, we show the development of a novel composite material with crosslinked azobenzene LC polymer (PAzo) and poly (dimethylsiloxane) (PDMS) aiming at the improvement of photomobile polymer materials in mechanical properties. The composite films were prepared by photopolymerisation of azobenzene monomers in PDMS elastomers. By forming phase separated structure, in which PAzo chains were dispersed in PDMS matrix, fracture strain of photomobile polymer materials was significantly enhanced. The composite film showed macroscopic bending upon irradiation with UV light. This result implies that PAzo domains in polymer matrix can work as microactuators to afford macroscopic deformation of the whole film. The further improvement of this system in photomechanical properties would be feasible through adequate control of composition and the alignment of mesogens.[GRAPHICS].

DOI： 10.1080/02678292.2018.1516822

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Janus/gradient actuating materials have become promising candidates for actuating devices. The fabrication of functional Janus gradient actuators remains a challenge. This paper presents a facile fabrication of a hydrophilic/hydrophobic Janus inverse opal actuator via gradient infiltration. The Janus characteristics of the fabricated actuator were attributed to gradient infiltration along the thickness of the film caused by the gradient light intensity and the distinct polymerization behavior of ionic liquids and methyl methacrylate in the methanol system. The Janus film demonstrated directional bending upon water vapor adsorption, with a bending angle approaching 1440 in 4 s, accompanied by structure color/optic signal alteration. The actuating behaviors were effectively modulated by changing the composition of the film and the solvent system. Promising applications of this Janus solvent actuator were demonstrated in two sets of tests: driving an engine and lifting cargo. This work provides insight into the design and fabrication of multifunctional humidity-actuating materials.

DOI： 10.1021/acsnano.8b05758

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

We prepared 2 types of crosslinked liquid-crystalline polymers (CLCPs) (polyacrylates) with the same side-chain length but a different position of an azobenzene moiety in the side chain. We evaluated photoinduced deformation behavior of the CLCP films and photoisomerization behavior of azobenzene in the films at cryogenic temperature. Azobenzene moieties in both CLCP films showed no trans-cis isomerization and neither film exhibited bending behavior upon irradiation with UV light in liquid nitrogen [77 K]. On the other hand, when the film included azobenzene with a long spacer and a short tail, cis-trans isomerization of azobenzene and photoinduced deformation were observed in liquid nitrogen.

DOI： 10.1080/15421406.2019.1595490

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Poly(4-vinylpyridine) (P4VP) brushes were grafted onto a substrate via Cu(0)-mediated atom transfer radical polymerization and 1-pyrenebutyric acid (PBA) was incorporated into the brushes through hydrogen bonding interactions with P4VP by immersing the resulting substrate in PBA solution. Fluorescence measurements performed on the substrate after immersion showed that PBA units formed excimers even after the substrate was rinsed with dichloromethane, which confirms the formation of hydrogen bonds between pyridyl groups in the P4VP brushes and carboxyl groups of PBAs.

DOI： 10.1080/15421406.2019.1595484

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We prepared crosslinked azobenzene main-chain liquid-crystalline polymers (MCLCPs), in which the exchange of crosslinks can be brought about by transesterification reactions. The exchangeable crosslinks enable reshaping and self-healing of the MCLCPs upon heating. Furthermore, the stress generated by stretching the MCLCP film is completely relaxed at 180 degrees C through rearrangement of networks. The film after hot-drawing shows reversible bending behavior upon irradiation with UV and visible light.

DOI： 10.1080/15421406.2019.1595482

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A reversible solvent-sensitive actuator with a continuous bending/debending process is fabricated by over-infiltration of liquid crystal monomers into a colloidal template and subsequent photopolymerization. The fabricated actuator exhibits a maximum bending angle of 1080 degrees in 1.58 s in dichloromethane, accompanied with successive debending in 0.32 s. The behavior of the actuator can be modulated by changing the solvent type, film thickness/length and molar ratio of A6OCB/C6M. This study will provide an important experimental and theoretical basis for the development of novel actuators.

DOI： 10.1039/c8sm00927a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The large-area formation of functional micropatterns with liquid crystals is of great significance for diversified applications in interdisciplinary fields. Meanwhile, the control of molecular alignment in the patterns is fundamental and prerequisite for the adequate exploitation of their photoelectric properties. However, it would be extremely complicated and challenging for discotic liquid crystals (DLCs) to achieve the goal, because they are insensitive to external fields and surface chemistry. Herein, a simple method of patterning and aligning DLCs on flat substrates is disclosed through precise control of the formation and dewetting of the capillary liquid bridges, within which the DLC molecules are confined. Large-area uniform alignment occurs spontaneously due to directional shearing force when the solvent is slowly evaporated and programmable patterns could be directly generated on desired substrates. Moreover, the in-plane column direction of DLCs is tunable by slightly tailoring their chemical structures which changes their self-assembly behaviors in liquid bridges. The patterned DLCs show molecular orientation-dependent charge transport properties and are promising for templating self-assembly of other materials. The study provides a facile method for manipulation of the macroscopic patterns and microscopic molecular orientation which opens up new opportunities for electronic applications of DLCs.

DOI： 10.1002/smll.201800557

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

This paper demonstrates multi-functional optical properties of organosilane-polymerized carbon dot inverse opals, such as tricolor-fluorescence, fluorescence enhancement, multi-color micro-patterns for anti-fake applications and a thermally-induced blueshift of bandgaps. It is of significance for the design and fabrication of novel optical devices.

DOI： 10.1039/c7nr09387j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Inc.  

Crosslinked liquid-crystalline polymers (CLCPs) containing azobenzene moieties show reversible macroscopic deformation upon irradiation with light. The deformation of CLCPs strongly depends on alignment of mesogens. Therefore, it is desirable that the alignment of mesogens in CLCPs can be freely controlled even after crosslinking. We successfully realigned the mesogens in CLCPs with the aid of dynamic covalent bonds to accomplish this challenge. In this study, we prepared CLCP films containing dynamic covalent bonds and photoalignable azobenzene moieties. Photoalignment of the films was performed by irradiation with linearly polarized UV light at 120°C. The films after photoalignment showed bending behavior along the direction in which the mesogens had been realigned by photoalignment when irradiated with unpolarized UV light. This result indicates that alignment of mesogens in the films changes before and after photoalignment even after crosslinking.

DOI： 10.1080/15421406.2018.1466242

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We developed a novel block copolymer composed of poly(ethylene oxide) (PEO) and polymethacrylate functionalized with liquid-cryst-alline oligothiophene by using the atom transfer radical polymerization (ATRP), aiming at application to organic photovoltaic (OPV) cells. Thermal investigation showed that the resultant polymer exhibits liquid-crystalline phases both on heating and cooling. Morphologies of the thin films of the block copolymer were investigated by atomic force microscopy (AFM). Microphase separation with a small size of almost 10nm (nano-phase-separated structures) was observed upon annealing.

DOI： 10.1080/15421406.2018.1466243

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Language：English   Publishing type：Part of collection (book)   Publisher：wiley  

DOI： 10.1002/9781119123279.ch1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

This paper presents a unique morphological evolution of metal-organic inverse opals (Pb(NO3)(2)-poly(St-MMA-AA)) subjected to an electrowetting process. The morphology of the building blocks changes from interconnected pores to separated hollow spheres during the electrowetting process, accompanied by an unusual blue-shift of the stopband position and the decreased wettability of the film. This morphology evolution is attributed to the simultaneous collapse/reconstruction of the metal-organic frame owing to the partial dissolution of the metal salt and the interfacial assembly of the metal-organic coordination around the skeleton. The adjustable morphology can be developed as a novel and simple water-lithography approach for the creation of the photonic crystal pattern.

DOI： 10.1002/adfm.201605221

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

We developed photomobile polymer materials with interpenetrating polymer network (IPN) structures composed of crosslinked liquid-crystalline azobenzene polymer (PAzo) and poly(dimethylsiloxane) (PDMS). By introducing PDMS into a PAzo template network, IPN was formed without disturbing the alignment of mesogens in the PAzo network. The films showed macroscopic bending behavior upon irradiation with UV and visible light. Although the IPN film showed a phase separated structure, the bending speed was significantly enhanced compared with the pristine film of PAzo, thanks to the soft nature of PDMS. The present method of preparing IPNs can be a promising approach to combine PAzo with various polymers and enhance the mechanical and photoresponsive properties.

DOI： 10.1039/c7sm01412k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Incorporation of dynamic covalent bonds into photomobile liquid-crystalline elastomers with a polysiloxane backbone enables the alignment of mesogens and macroscopic shapes to be controlled through the rearrangement of the network topology, even after the formation of chemically crosslinked networks. The reshaped samples show various sophisticated 3D motions upon irradiation with UV and visible light, depending on their initial shapes.

DOI： 10.1002/adma.201602745

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Crosslinked liquid-crystalline polymers (CLCPs) show unique behavior of deforming macroscopically when stimulated with heat, electricity and light. However, they cannot be remolded and reshaped once prepared. Here, we designed crosslinked polysiloxane with side chain mesogens that contain exchangeable crosslinking points based on transesterification between phenyl benzoates and hydroxy groups. After the formation of a polymer network, a base catalyst was introduced into the CLCP. When heated at 80 degrees C, a piece of the CLCP was reshaped into a film and separate pieces of the CLCP were fused together, indicating that the CLCP is remoldable.

DOI： 10.1080/15421406.2015.1049910

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Cross-linked liquid-crystalline (LC) polymers with a mesomorphic diarylethene were prepared to demonstrate a versatile strategy for cross-linked photochromic LC polymers as photomobile materials. Upon exposure to UV light to cause photocyclization of the diarylethene chromophore, the cross-linked polymer films bend toward an actinic light source. By irradiation with visible light to cause a closed-ring to open-ring isomerization, the bent films revert to the initial flat state. Without visible-light irradiation, the bent films remain bent even at 120 degrees C, indicating high thermal stability of the cross-linked diarylethene LC polymers.

DOI： 10.1002/chem.201406299

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We studied the photo-induced dynamics in a LC polymer film including azobenzene by using a time-resolved and a microscopic technique. The film was confined in a liquid crystal cell, while it is a photomobile film under a free standing condition, which is triggered by the photoisomerization of azobenezene. From the result of the time-resolved measurements, the change inside the film induced by UV irradiation was highly anisotropic polarization change. Microscopic observation revealed that the film was consisted of ordered and disordered region with a patched structure, and the UV induced change was travelled in the ordered region on the order of seconds.

DOI： 10.1117/12.2186414

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Crosslinked liquid-crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction-expansion and bending-unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field.

DOI： 10.1002/anie.201400513

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We prepared photomobile polymer materials composed of crosslinked azobenzene liquid-crystalline polymers (LCPs) and methacrylates with interpenetrating polymer network (IPN) structures, and explored their photoresponsive behavior. The IPN films exhibited reversible bending upon photoirradiation. In addition, the durability of the IPN films was much higher than that of the pristine crosslinked azobenzene LCP films.

DOI： 10.1080/15421406.2014.940491

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Cross-linked azobenzene liquid-crystalline polymer films with a poly(oxyethylene) backbone are synthesized by photoinitiated cationic copolymerization. Azobenzene moieties in the film surface toward the light source are simultaneously photoaligned during photopolymerization with unpolarized 436 nm light and thus form a splayed alignment in the whole film. The prepared films show reversible photoinduced bending behavior with opposite bending directions when different surfaces of one film face to ultraviolet light irradiation.

DOI： 10.1002/marc.201400112

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Mechanical properties of flexible films, for example surface strain of largely bending films, are key to design of stretchable electronic devices, wearable biointegrated devices, and soft microactuators/robots. However, existing methods are mainly based on strain-gauge measurements that require miniaturized array sensors, lead wires, and complicated calibrations. Here we introduce a facile method, based on surface-labelled gratings, for two-dimensional evaluation of surface strains in largely bending films. With this technique, we demonstrate that soft-matter mechanics can be distinct from the mechanics of hard materials. In particular, liquid-crystalline elastomers may undergo unconventional bending in three dimensions, in which both the inner and outer surfaces of the bending film are compressed. We also show that this method can be applied to amorphous elastomeric films, which highlights the general importance of this new mechanical evaluation tool in designing soft-matter-based electronic/photonic as well as biointegrated materials.

DOI： 10.1038/srep05377

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Various fabrication methods of photomobile polymer materials containing photochromic moieties have been developed to improve their photoresponsive and mechanical properties. Here, we newly prepared photomobile polymer materials with interpenetrating polymer network (IPN) structures. The IPN films, which are composed of azobenzene liquid crystalline polymer (LCP) and polymethacrylates, showed reversible bending behavior upon exposure to UV and visible light. Bending speed of the IPN films became higher with decreasing glass-transition temperature of polymethacrylate components. The IPN film containing poly(dodecyl methacrylate) showed faster bending than the pristine azobenzene LCP film.

DOI： 10.1080/15421406.2014.917479

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer Japan  

An organic semiconductor is material that is capable of transporting a charge, that is, electrons and holes. By this characteristic, that is, the property to support a current flow, they can be used in various electronic devices. In the early 1970s, organic semiconductors have been put to their first practical use in the photosensitive drum of copy machines. Thereafter, it began to be used as a practical material for organic electroluminescent (EL) elements in the 1990s. In recent years, research and development has been actively aimed to practical use in organic solar cells and organic transistors.

DOI： 10.1007/978-4-431-54859-1_11

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Uniaxially aligned azobenzene liquid-crystalline polymers crosslinked by hydrogen bonding can deform in response to actinic light. The polymers can be precisely shaped due to high processability of hydrogen-bonded polymers. The mechanical properties of the polymer fibers were improved by introducing single-walled carbon nanotubes as a filler material. Because of weak hydrogen bonding, starting materials can be recovered, reused and recycled, which is very useful in view of chemical resource utilization.

DOI： 10.1039/c3tc32585g

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We studied the effect of the ratio between the monomer and cross-linker molecules in the azobenene included liquid crystal polymer films by using the heterodyne transient grating (HD-TG) technique, which is one of the time-resolved measurement techniques. Depending on the ratio, the magnitude of the refractive index change, its anisotropy, and the lifetime of the cis isomer of azobenzene, generated by a UV pulse irradiation. By increasing the cross-linker ratio, the refractive index change and its anisotropy was reduced, indicating less ability for the motion, while slower lifetime was observed by increasing the monomer ratio, indicating that the film is difficult to return the original shape by a visible-light irradiation. The obtained dynamics was consistent with the functionality of the films.

DOI： 10.1117/12.2059740

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

By using the depth selective imaging method, we studied the UV induced change in a photomobile liquid crystalline polymer film. With 1 mu m depth resolution, each slice inside the film was selectively observed. A network-like structure mixed with the ordered and disordered regions of molecules in the middle of the film, and a rubbed polymer layer at the bottom of the film were observed. In each slice of the film, the phase change induced by UV light was observed strongly dependent on the director direction, which indicates the ordering change of the liquid crystalline molecules in the director direction. It took several tens of seconds for the ordering change caused by the collaborative interaction between the molecules. Furthermore, it was suggested that the UV induced change travelled from the bottom layer to the middle layer on the micron order.

DOI： 10.1039/c4cp04602a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The synthesis and characterization of organic nanoparticles composed of a polymer network of azobenzene moieties and capable of reproducible, photoinduced mechanical actuation are reported. The molecules within the nanoparticles undergo co-ordinated, reversible isomerization between cis- and trans-conformations in response to ultraviolet and visible electromagnetic radiation, resulting in a reversible 20% height contraction of nanoparticles adsorbed on a substrate. The kinetics of the actuation response as a function of light intensity and duration are reported and closely match the molecular kinetics of azobenzene photoisomerization. The results support the proposed mechanism of co-ordinated molecular conformational changes resulting in observable nanoscale actuation.

DOI： 10.1002/macp.201200581

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We present a simple way to control the photoinduced-bending direction of azobenzene-containing cross-linked liquid-crystalline polymers. By changing the location of the photoactive azobenzene moieties from cross-links to side-chains, the bending direction of the sample is reversed under identical irradiation conditions. In addition to providing a versatile route toward directionality control of the photoinduced macroscopic motions, this observation highlights the complicated nature of the photomechanical response of azobenzene-containing cross-linked liquid-crystalline polymers, showing that the photomobile behavior can be determined by seemingly small details on the materials design.

DOI： 10.1021/mz200056w

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Organic light-emitting diodes (OLEDs) based on chromophore-containing liquid crystals (LCs) can emit polarized light due to self-assembly of mesogenic chromophores. The stability of LC phases in LC polymers with a mesogenic group in the main chain is higher than that in the polymers containing a mesogenic group in the side chain.In this study, a novel family of polyesters containing a carbazole moiety as a hole-transporting unit and an oxadiazole (OXD) moiety as an electron-transporting unit in the main chain, P10-DOXDCz and P16-DOXDCz, were designed and synthesized. These polyesters were prepared by transesterification of N-hexyl-3,6-di[2-([1,3,4] oxadiazol-5-yl)- 4-methylbenzoate] carbazole and 1,10-decanediol or 1,16-hexadecanediol at 220 degrees C for 20 h. They showed a nematic phase. Both P10-DOXDCz and P16-DOXDCz emitted intense blue fluorescence with a maximum at 439 nm and 450 nm in thin films, respectively, and their fluorescence quantum yields were 0.74 and 0.81 in solution, respectively. Both compounds exhibited polarized emission in a LC phases, and the order parameters estimated from the polarized emission spectra were 0.10 for P10-DOXDCz and 0.14 for P16-DOXDCz. Fabricated devices, ITO/PEDOT:PSS/P10-DOXDCz and P16-DOXDCz/MgAg, emitted blue light when a positive voltage was applied to the ITO electrode.

DOI： 10.1080/15421406.2012.688625

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Organic light-emitting diodes (OLEDs) based on conjugated polymers exhibiting polarized emission have attracted much attention because of their potential as backlights for conventional liquid crystal (LC) displays and 3-D displays. We have reported a new series of LC polymers based on donor-acceptor architecture containing an oxadiazole (OXD) and several amine moieties in the same side chain, which exhibit bipolar character with a wide energy band gap.In this study, to develop phosphorescent OLEDs with polarized emission, we synthesized a platinum complex, Pt(4-decyloxy) salen, with emitting property, and fabricated the device consisting of Pt complex as a guest and LC polymers as a host material. The Pt complex exhibited high thermal stability, good solubility and an emission peak at 530 nm in dichloromethane. To obtain electroluminescense from the Pt complex, we fabricated ITO/rubbed PEDOT:PSS/Pt(4-decyloxy) salen: host polymer/MgAg devices. The devices emitted a yellowish green light, which was dominated by the triplet emission of the platinum complex. In addition, polarized electroluminescence was observed in an aligned LC polymer film.

DOI： 10.1080/15421406.2012.688619

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

We have investigated the photoresponsive behavior of homogeneously aligned low-azobenzene-concentration crosslinked liquid-crystalline polymers. We compared the thermal contraction and photocontraction of the films, and show that upon UV irradiation, they bend efficiently towards the actinic light source. The photoinduced bending is studied both under continuous-wave irradiation and irradiation with nanosecond pulses. Pulsed irradiation revealed that the photomechanical response can take place within sub-millisecond time scale, and that even a single laser pulse can cause the sample to bend.

DOI： 10.1142/S0218863511006200

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The photomechanical behavior of cross-linked azobenzene-containing liquid-crystalline polymer films was investigated by means of simultaneous measurement of their optical and mechanical properties. The connection between photoisomerization of the azobenzene moieties, photoinduced change in molecular alignment, photoinduced stress generation, and macroscopic bending was analyzed. Upon UV irradiation, the films exhibited bending due to gradient in cis-azobenzene content, and subsequent unbending when cis-azobenzene content became uniform throughout the film. The maximum photoinduced stress was generated in the same time scale as the time required to reach photostationary state in the cis-azobenzene concentration. The maximum values of photogenerated stress strongly depended on the crosslinker concentration, even if the azobenzene concentration and the cis-azobenzene content in the photostationary state were similar for all the polymer films. The stress is connected to the initial Young's modulus and also to the photoinduced change in birefringence of the polymer films. In addition, a significant photoinduced decrease in Young's modulus was for the first time observed in cross-linked azobenzene-containing liquid-crystalline polymers, which is likely to be an important factor in dictating their photomechanical behavior.

DOI： 10.1021/am200621j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Modern society is based on the production of energy, primarily, from fossil fuels; however, these resources are limited. Therefore we are now confronted with a difficult problem: producing energy without burning fossil fuels. Many countries have utilized nuclear power to generate electricity as an effective source of energy, such as the US, France, and Japan. However, the tragic disaster at the Fukushima nuclear power station has reminded us that nuclear power is a double-edged sword: it may be a useful energy source, but it can bare its fangs when we lose control. We have many natural energy sources that are present in unlimited quantities, and so are unlikely to be exhausted easily: namely, sunlight, water, and wind. It is thus timely to consider further developing these natural resources to replace nuclear power for the production of energy.

DOI： 10.1016/S1369-7021(11)70212-7

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Language：English   Publishing type：Part of collection (book)   Publisher：CRC Press  

Liquid crystals (LCs) represent thermodynamically stable phases situated conceptually between an ordinary isotropic liquid and a crystalline solid. Due to a fact that LCs possess simultaneously the optical anisotropy of crystals and the fluidity of liquid, they showmany exclusive properties (optical, electrical, andmagnetic) and alignment changes by external fields at surfaces and interfaces [1]. Control of theLC alignment is the most important technology in most devices using LCs as active media. Especially, alignment of nematic LCs can be easily changed and controlled by weak external fields. It is suggested that cooperative motion of LCs may be most advantageous in changing the alignment of LC molecules by external stimuli. If a small portion of LC molecules change their alignment in response to an external stimulus, the other LC molecules also change their alignment. This means that only a small amount of energy is needed to change the alignment of whole LC molecules: such a small amount of energy as to induce an alignment change of only 1 mol% of LC molecules is enough to bring about the alignment change of the whole system [2].According to this principle, photomanipulation of the LC alignment has also been reported for polymer films containing photochromic molecules such as azobenzenes, in which a small amount of azobenzene molecules change their shape by light and then the cooperative change of LC alignment takes place [2]. Photoalignment of LCs has attracted much attention due to its high light sensitivity and large change in refractive index. The effects of structure and density of azobenzene molecules on the photoalignment have been explored systematically [3].

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Azobenzene liquid-crystalline (LC) polymers coated on a flexible polymer substrate were directly crosslinked by electron beams (EBs). We demonstrated that EB-crosslinked azobenzene LC polymers could successfully work as photomobile polymer materials with an adhesive-free bilayer structure.

DOI： 10.1039/c0jm03901b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Irradiation at room temperature of alpha,omega-di-[4-cyanophenyl-4'-(6-hexyloxy)-azobenzene]-poly-(N-isopropylacrylamide) (Az(2)-PNIPAM) solutions in water/1,4-dioxane (6 mol% dioxane) reversibly converts a turbid suspension into a clear solution, demonstrating for the first time that cononsolvency of PNIPAM in mixed aqueous solvents in synergy with preferential chromophore solvation can act as actuators of responsive systems.

DOI： 10.1039/c0cc04009f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Crosslinked azobenzene liquid-crystalline polymer films have been prepared by in-situ photopolymerization, and their photoinduced changes in birefringence and stress on macroscopic motion were investigated. Upon exposure to UV light, the film bent toward an actinic light source along the rubbing direction, and the bent film also reverted to the initial flat state after exposure to visible light at room temperature. Moreover, the birefringence simultaneously decreased and the stress was generated upon UV irradiation. These results indicate that the molecular alignment in the film becomes disordered by trans-cis photoisomerization of the azobenzene moieties and the resultant contraction of the film generates the stress.

DOI： 10.1080/15421406.2011.600213

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We prepared crosslinked azobenzene liquid-crystalline polymer brushes on flexible polymer films by surface-initiated atom transfer radical polymerization and a subsequent crosslinking reaction. Reversible isomerization of azobenzene moieties was observed in the crosslinked films upon irradiation with UV and visible light. Upon exposure to linearly polarized UV light, the films bent slightly along the polarization direction of light toward an actinic light source. After turning off the UV light, the films maintained the bent shape, and then reverted to the initial form by irradiation with visible light. We have successfully developed a novel photomobile material with crosslinked azobenzene liquid-crystalline polymer brushes.

DOI： 10.1080/15421406.2011.572809

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Crosslinked liquid-crystalline polymer fibers containing azobenzene moieties show three-dimensional movements under photoirradiation (see figure). The direction of the photomobility of the fibers could be controlled by manipulating the actinic light source. The generated stress upon photoinduced bending reached 210 kPa, which is similar to the stress in human muscles.

DOI： 10.1002/adma.200902879

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We proposed a new approach to fabricate bilayer films with a crosslinked azobenzene liquid-crystalline (LC) polymer. The polyethylene (PE) substrates were coated with linear azobenzene LC polymers, and then the azobenzene layers were crosslinked by irradiation with electron beams (EBs). In the EB-irradiated films with ordered azobenzene moieties, exposure to UV light caused trans-cis isomerization and the change in alignment of azobenzene moieties. Bending of the bilayer films could be induced toward an actinic light source when they were irradiated from the side of the azobenzene layer, while they bent away from the actinic light source upon UV irradiation from the side of the PE layer. In both cases, the bent films reverted to the initial flat state by turning off the light, which could be repeated at room temperature.

DOI： 10.1080/15421406.2010.495897

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We studied the effects of concentration and location of azobenzene chromophores on the photoinduced deformation of crosslinked liquid-crystalline polymers (CLCPs). The concentration of azobenzene chromophores in CLCP affects the degree of isomerization of azobenzene moieties and the macroscopic deformation behaviour of the films while the location of azobenzene moieties determines the contraction force and length.

DOI： 10.1039/b917342k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Crosslinked liquid-crystalline polymer films with a different content of an azobenzene moiety were prepared by in-situ photopolymerization, and their photoresponsive behavior was investigated. Observation of the films by polarized absorption spectroscopy and polarizing optical microscopy has revealed that the azobenzene moieties are aligned along the rubbing direction in the films. Upon irradiation with UV light, a film with 5mol% of the azobenzene bent toward an actinic light source along the rubbing direction. The bent film reverted completely to the initial state upon irradiation with visible light. On the other hand, films with 3 and 1mol% of the azobenzene showed no obvious bending by continuous irradiation with UV light. The bent film also reverted to the flat state upon continuous irradiation with UV light.

DOI： 10.1080/15421406.2010.495676

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

A telechelic poly(N-isopropylacrylamide) (PNIPAM) with azobenzene end-groups (telechelic Az-PNIPAM) was prepared by reversible addition-fragmentation chain transfer (RAFT) free radical polymerization of NIPAM. This polymer self-assembles in cold water forming nanoparticles with a hydrodynamic radius (RH) of 8nm and an aggregation number of 29 chains. The thermoresponsive behavior of Az-PNIPAM in water was investigated by turbidimetry and light scattering. In addition, the photoresponsive behavior of aqueous Az-PNIPAM was investigated by monitoring the changes with temperature of the solution and transmittance at 650nm before and after irradiation at 366nm.

DOI： 10.1080/15421406.2010.495899

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Isomerization polymerization of 4-alkylcyclopentenes catalyzed by Pd-diimine complexes produces the polymers with trans-1,3-disubstituted cyclopentane rings located regularly along the polymer chain. The polymers with isotactic structure formed by using a C-2-symmetric catalyst exhibited liquid-crystalline properties.

DOI： 10.1021/ja904150w

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The composition of a crosslinked azobenzene liquid-crystalline polymer and a flexible polymer film can provide a variety of simple devices that can walk in one direction like an 'inchworm' and move like a 'robotic arm' induced by light.

DOI： 10.1039/b815289f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

To precisely control the first-order diffraction efficiency of holographic gratings recorded in an amphiphilic diblock liquid-crystalline copolymer P40A37, effect of recording time on grating formation and enhancement was studied systematically. Several parameters such as surface relief, the first-order diffraction efficiency, the maximum transmittance under an optical polarizing microscope and order parameters of grating samples were evaluated before and after annealing. Then the enhancement coefficient with recording time was estimated. The best enhancement effect was obtained at 10-s recording upon nano-scaled phase separation. By precisely adjusting the recording time, the diffraction efficiency of holographic gratings in P40A37 can be finely controlled from 0.13% to 10%.

DOI： 10.1080/15421400802612094

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We prepared homogeneously aligned azobenzene liquid-crystalline elastomer (LCE) films with low Tg and explored their photomechanical properties. Upon irradiation with UV light, the films bent toward a light source at room temperature. The mechanical force generated upon exposure to UV light was evaluated by thermomechanical analysis. It was found that the mechanical force generated by photo-irradiation increased with an increase in the cross-linking density. In particular, an LCE film containing 80 mol% azobenzene cross-linker produced a force of over 1 MPa by photo-irradiation, which enabled the film to lift an object 20 times heavier than itself. The degree of contraction by photo-irradiation increased with an increase in temperature and light intensity. Bending could be brought about by more than 5000 times with periodic irradiation. Furthermore, it was found that the LCE films exhibited bending and unbending behaviour by irradiation with sunlight.

DOI： 10.1080/02678290903138711

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Fabrication of a microlens array film was explored by means of photoinduced reorientation of dye-doped polymerizable liquid crystals (LCs). LC monomer/photoinitiator mixtures doped with a small amount of an oligothiophene derivative were irradiated with a 488-nm beam from an Ar+ laser. Then the sample cell was periodically moved. After these two processes were repeated for a few tens times, remaining photoinitiators were quenched by irradiation with UV light. Observation of the cells with a polarizing optical microscope revealed that the molecular alignment of LCs induced by the Ar+ laser beam remained unchanged after the beam was turned off and a microlens array with a square-lattice type was obtained. This indicates that formation of the microlens and photopolymerization of the LC monomers are brought about simultaneously in a small area. The fabricated microlens has polarization selectivity that reflects molecular alignment. The focal length of the microlens arrays could be changed by controlling the irradiation intensity. Furthermore, a freestanding film with microlens arrays was obtained by peeling from the sample cell.

DOI： 10.1080/15421400903054394

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Two azobenzene-containing block copolymers with an oxyethylene (P1) or an alkyl (P2) spacer in the side chain were prepared by atom transfer radical polymerization (ATRP). Neither of the block copolymers with a low azobenzene content showed a liquid-crystalline phase. However, their glass transition temperatures (T(g)s) were lowered by introducing flexible spacers. In particular, T-g was lowered by about 30 degrees C in P1. Their photoalignment and holographic behavior was investigated at various temperatures in thin films. Rapid changes in refractive index were induced in the P1 films upon irradiation at a temperature below T-g. But the photoinduced birefringence in the P1 film was lower than that in the P2 films. Similar results were obtained in holographic recording. The azobenzene-containing block copolymer with the oxyethylene spacer (P1) used in this study has potential application for dynamic hologram.

DOI： 10.1080/15421400903196120

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

A block copolymer containing an azobenzene (Az) moiety in the side chain was prepared by atom transfer radical polymerization (ATRP). For comparison, a random copolymer with a similar Az content was also designed. Their photoresponsive and holographic behavior was investigated in thin films. The block copolymer film showed microphase separation with cylinder microdomains after annealing, which was then irradiated at 366 nm. It was found that trans-cis photoisomerization in the block copolymer film was slower than that in the random copolymer film. This may be due to the restricted motion of the Az moieties in the Az blocks. The photoinduced birefringence (Delta n) of the block copolymer film was higher than that of the random copolymer film upon irradiation with a linearly polarized beam. In holographic recording, similar results were obtained. A block copolymer with 22-mol% Az showed a liquid-crystalline (LC) phase, while a random copolymer with 24-mol% Az exhibited no LC phase. The block copolymer showed an LC phase at a lower Az content compared with the random copolymer, suggesting that the molecular alignment of Az mesogenic groups is enhanced by cooperative motion of LCs in block copolymer films.

DOI： 10.1080/15421400802615105

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Laminated films composed of a flexible plastic sheet and a crosslinked azobenzene liquid-crystalline polymer (CLCP) layer with different initial alignment of azobenzene mesogens were prepared by thermal compression bonding of a CLCP film and an unstretched low-density polyethylene (PE) film with an adhesion layer. In both laminated films with a homogeneous alignment of mesogens and a homeotropic one, large movements could be induced by irradiation with UV light at room temperature. A partly laminated film with homogeneous CLCP bent from both ends of the whole film, while one with homeotropic CLCP bent up from the center of the film toward the light source. These results indicate that we enable plastic films with no photoresponsive property to move flexibly upon photoirradiation just by laminating the CLCP layers partly, and the photoinduced motions of the laminated films are completely dependent on the alignment direction of the mesogens in the CLCP layers. In addition, it was found that the maximum stress generated in the films and the stress increment are also different between the homogeneous CLCP laminated films and the homeotropic ones.

DOI： 10.1080/15421400802612391

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Blue-emitting polymers based on a donor-acceptor architecture composed of oxadiazole and carbazole moieties containing various substituted groups in the same side chain were used as a host polymer in phosphorescent polymer light-emitting diodes (PhPLEDs). The polymer containing N-methylcarbazole showed a liquid-crystalline (LC) phase above its glass transition temperature but the other polymer containing N-ethylhexylcarbazole exhibited an amorphous phase. The single-layer PLEDs using these polymers exhibited blue emission with peaks from 430 to 440 nm. To examine the LC polymer (LCP) and the amorphous polymer as host materials, we fabricated simple devices using Ir(ppy)(3) and (btp)(2)lr(acac) as phosphorescent dopants at various doping concentrations. The device composed of lTO/PEDOT-PSS/2wt% of (btp)(2)Ir(acac) doped into LCP/MgAg showed intense red light (0.67, 0.32) with the luminance efficiency of 4.7 cd/A. The luminance efficiency of the PhPLEDs using the LCP was higher than that of the PhPLEDs using the amorphous polymer.

DOI： 10.1080/15421400903196138

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A series of liquid-crystalline (LC) diblock copolymers with an azobenzene moiety in the side chain were prepared by atom transfer radical polymerization (ATRP). Using a bromo-terminated poly(methyl methacrylate) as a macroinitiator, the obtained diblock copolymers showed well-defined structures and narrow molecular-weight distributions. Microphase-separated nanostructures with mesogenic blocks in either continuous or separated phases were observed. Owing to varied content of mesogens in the block copolymers, they showed different behavior of photoinduced alignment and holographic recording. Block copolymers with azobenzenes in the majority phases exhibited a similar performance of photoinduced alignment and refractive-index modulation to the azobenzene-containing homopolymer, but their photoinduced mass transportation was partly suppressed by the microphase separation, leading to a lower surface relief than that of the homopolymer. The photoinduced mass transfer was greatly prohibited in the block copolymers with mesogenic groups in the minority phases, resulting in little surface relief. However, refractive-index gratings were still recorded upon local alignment, driven by the photoinduced alignment of azobenzenes or the phototriggered molecular cooperative motion between azobenzenes and nonphotosensitive cyanobiphenyl groups. Then the possible schematic illustrations of mesogens and microphase separation in the grating structures were proposed.

DOI： 10.1021/ma801077g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ma802119d

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Language：English   Publishing type：Part of collection (book)   Publisher：John Wiley & Sons, Inc.  

DOI： 10.1002/9780470439098.ch12

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Language：English   Publishing type：Part of collection (book)   Publisher：John Wiley & Sons, Inc.  

DOI： 10.1002/9780470439098.ch3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We present a simple method to record subwavelength gratings (SWGs) in an azobenzene (AZ)-containing liquid-crystalline polymer by preirradiation. Since the cooperative motions of mesogens are eliminated in a cis-AZ-rich isotropic phase by the pretreatment, the subwavelength modulation of surface relief and refractive index (RI) was obtained. The surface relief of less than 10 nm and the RI modulation were detected by atomic force microscopy. A large phase retardation and formed birefringence were obtained in the recorded SWGs in which a possible schematic illustration of AZ was proposed. (C) 2008 American Institute of Physics.

DOI： 10.1063/1.2894073

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

An amphiphilic block copolymer composed of poly(ethylene oxide) and poly(methacrylate ester) bearing a donor-acceptor-type 2,5-diarylthiazole in the side chain is prepared by atom-transfer radical polymerization. The precursor 2,5-diarylthiazole monomer is prepared by transition-metal-catalyzed CH arylation reactions. A thin film of the block copolymer formed by spin coating exhibited nanoscale phase separation with homeotropically oriented domains, while a film formed by the friction transfer method showed domains with homogeneous orientation confirmed by AFM. Spectroscopic studies of the film, utilizing the luminescent characteristics of 2,5-diarylthiazole, showed polarized light emission as a result of the liquid crystalline ordering.

DOI： 10.1246/cl.2008.272

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

(t-BuNSiMe(2)Flu)TiMe(2) (1) activated with Me(3)Al-free methylaluminoxane (dried MAO) which conducts vinyl addition polymerization of norbornene (N) with very high activity was applied for homopolymerization of N derivatives (i.e., 5-vinyl2-norbornene (5V2N), 5-ethylidene-2-norbornene (MN), dicyclopentadiene (DCPD)) at 40 degrees C. The activities for the N derivatives were about two orders of magnitude lower than that for N and decreased in the following order: 5E2N > 5V2N > DCPD. Copolymerization of ethene (E) and 5E2N under an atmospheric pressure of E was then conducted by 1-dried MAO. The copolymerization proceeded with better activity than the homopolymerization of 5E2N and gave poly(E-co-MN) with narrow molecular weight distribution. The content of the ethylidene group in poly(E-co-5E2N) was controlled by the feed ratio of 5E2N/E. The T(g) value of the copolymer changed from 70 degrees C to 155 degrees C according to the 5E2N content from 27 mol % to 68 mol %. The addition of N as a third monomer to the E-5E2N copolymerization improved the activity and raised the Tg values of the terpolymer above 200 degrees C. The content of 5E2N was controlled by the 5E2N/N ratio with keeping the high Tg values. (c) 2007 Wiley Periodicals, Inc.

DOI： 10.1002/pola.22193

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Bragg-type polarization holograms were recorded in thick copolymer films with tolane and azobenzene moieties by interfering two orthogonal circularly polarized beams at 488 rim. Observation of the films with a polarizing optical microscope revealed that circular alignment of molecules was induced along a grating vector. An incident reading beam at 633 nm was efficiently diffracted, depending on its polarization state and incident direction.

DOI： 10.1246/cl.2007.1146

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The synthesis and photopolymerization of alkaline-developable hyperbranched polyurethane (HBPUMA-COOH) were examined. The reaction of dicyclohexylmethane 4,4'-diisocyanate (CMDI) and trimethylolpropane (TMP) in the presence of 2-methacryloyloxyethyl isocyanate (MOI) was carried out to give the soluble hyperbranched polyurethane (HBPUMA) with terminal methacryloyl groups in satisfactory yield. After that, HBPUMA-COOH was synthesized by the reaction of HBPUMA and cis-1,2,3,6-tetrahydrophthalic anhydride (THPA). The photoradical polymerization of HBPUMA-COOH was examined in the presence of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-2-one (Irgacure 907) as a photoinitiator in the film state upon UV irradiation to afford the corresponding cured film quantitatively. It was found that the tensile strength of the resulting cured film of HBPUMA-COOH was higher than those of the HBPUMA and linear one. The negative patterning property of HBPUMA-COOH also had 5 mu m line and space pattern resolution by UV irradiation with 150 mJ/cm(2). Furthermore, it was cleared that the photocured HBPUMA and HBPUMA-COOH showed very low birefringence.

DOI： 10.1021/ma062381s

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Grating waveguide couplers with a flat surface were fabricated in an azobenzene liquid-crystalline polymer film by holographic lithography using Ar+ laser beams at 488 nm. When a probe beam at 633 nm was incident to one grating of a grating waveguide coupler, the beam propagated in the waveguide and an output beam came out from the other grating with the throughput coupling efficiency of approximate to 5%. Upon irradiation of the film between two gratings with UV light to cause trans-cis photoisomerization of the azobenzene moiety, the intensity of the output beam was repeatedly switched. It was found that the alternating irradiation at 366 and 436 nm induced reversible changes in the intensity of the guided probe beam.

DOI： 10.1002/marc.200700041

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/smll.200600724

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Novel wormlike nanostructures were self-assembled in bulk films of a well defined diblock copolymer with azobenzene moieties, which was prepared by atom transfer radical polymerization (ATRP). For comparison, a homopolymer with almost the same repeat units of azobenzene as those in the copolymer was also prepared. They both had well defined structures and exhibited a smectic liquid crystalline phase. Upon annealing the copolymer films, poly (methyl methacrylate) formed a matrix with excellent optical properties, and the azobenzene segment in the minority phase self-assembled into a wormlike mesogenic domain in the bulk films. Such block copolymer films exhibited stability and transparency by eliminating the scattering of visible light, indicating their potential application as photoresponsive functional materials. Although wormlike morphologies have been obtained in micelles from block copolymer solutions, to the best of our knowledge, such wormlike nanostructures have never been explored in bulk films.

DOI： 10.1002/marc.200600901

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Fabrication of microlens arrays (see figure) is explored using photoinduced reorientation of dye-doped liquid crystals and successive photopolymerization with a single laser beam by selecting a suitable photoinitiator. Each microlens in the microlens array exhibits polarization selectivity with respect to the incident polarized light, and the arrays can be arranged in desired patterns and with desired polarization directions.

DOI： 10.1002/adma.200601329

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

After being pre-treated upon irradiation of unpolarized light at 366 nm, an azobenzene-containing liquid-crystalline polymer film was photoinduced alignment by one linearly polarized laser beam at 488 nm, leading to a large birefringence of 0.21. Then holographic gratings were recorded in the pre-irradiated polymer films by interference of two coherent laser beams. Little surface relief was obtained by the holographic recording process, indicating that a refractive-index grating paid most of contributions to the diffraction efficiency. Because the cooperative motion of the azobenzene mesogens were eliminated in the cis-azobenzene-rich isotropic film by the pre-irradiation, multi-processes of the refractive-index gratings were successfully achieved. The obtained grating structures were clearly shown in the polarizing optical microscopic pictures, which were also verified by their diffraction patterns. The azobenzene-containing liquid-crystalline polymer used in this study has potential application in high-density information storage.

DOI： 10.1080/15421400701492788

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The use of a crosslinked azobenzene liquid-crystalline polymer (CALP) system for micro-integrated actuators becomes especially attractive. CALPs can deform. along the alignment direction of mesogens upon irradiation of UV/visible light owing to photochemical phase transition. In this study, to improve the bending speed, CALP films with a homogenous alignment on one surface and a homeotropic alignment on the opposite surface (hybrid alignment) were prepared and their bending behavior was investigated. The films showed photoinduced bending whose direction was determined by the surface alignment treatments and the bending speed was greatly enhanced upon irradiation from both surfaces of the film at the same time.

DOI： 10.1080/15421400701680952

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Three azobenzene acrylate monomers containing alkyl spacers of different length were synthesized. Thermodynamic and mesomorphic properties of the monomers were measured by differential scanning calorimetry and polarizing optical microscopy. A crosslinker with the undecyl spacer was also synthesized to prepare crosslinked liquid-crystalline polymer films by photopolymerization. Polarized UV spectra and polarizing optical micrographs demonstrated that the mesogens are aligned homogeneously in the films. Low glass transition temperature of the films enabled them to bend near room temperature upon UV irradiation. Besides, the films generally bent away from the light source before they at last bent towards the light irradiation.

DOI： 10.1080/15421400701492895

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We report the synthesis and physical properties of crosslinked liquid-crystalline polymer (CLCP) fibers consisting of a liquid-crystalline monomer and all acrylate monomer with a hydroxyl group that acts (is a reactive site for crosslinking. By differential scanning calorimetry, the CLCP fibers showed a glass transition temperature around 60 degrees C. Polarizing optical microscopy revealed that we obtained fibers with high orientation of mesogens along the fiber axis. The CLCP fibers showed deformations induced by heated the fiber to all isotropic phase.

DOI： 10.1080/15421400701681083

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Azobenzene-containing polymer, in which a change in birefringence can be induced by photoisomerization, is one of promising materials for holographic applications. To develop high-performance holographic materials using azobenzene polymers, it is necessary to prepare optically transparent thick films with capability of a large photoinduced change in refractive index to obtain high diffraction efficiency and fast response in the Bragg regime. A number of materials have been studied so far, but no attention has been paid to the combination of thick amorphous copolymers films containing photoresponsive and mesogenic groups in the side chain and polarization gratings formed in the Bragg regime. In this paper, we prepared optically transparent thick polymer films containing an azobenzene moiety with photosensitivity and a tolane moiety with high birefringence, and formed intensity and polarization gratings with linearly polarized beams and orthogonal circularly polarized beams, respectively. It was found that the nearly theoretically maximum diffraction efficiency was successfully achieved, and the recorded hologram could be erased thermally or photochemically. In addition, a large change in refractive index was induced in the polarization grating, and high diffraction efficiency (similar to 90%) and quick response (920 ms) was realized simultaneously.

DOI： 10.1117/12.722666

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN  

DOI： 10.2494/photopolymer.20.91

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In bulk films of a novel well-defined amphiphilic diblock liquid-crystalline copolymer with aramid moieties, a stable perpendicularly orientated hydrophilic nanocylinder array with hexagonal packing was formed in a large area by supramolecular self-assembly.

DOI： 10.1039/b705748b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The synthesis of donor-acceptor-type 2,5-diarylthiazoles that bear electron-donating NN-dialkylamine and electron-withdrawing cyano groups at the 2- and 5-position, respectively, were carried out with transition-metal-catalyzed C-H arylation reactions developed by us. The compounds were synthesized by the C-H arylation of unsubstituted thiazole at the 2-position with a palladium/copper catalyst in the presence of tetrabutylammonium fluoride (TBAF) as an activator. Further C-H arylation of the 2-arylated thiazole at the 5-position was carried out by the palladium-catalyzed reaction in the presence of silver(I) fluoride to afford the donor-acceptor-type 2,5-diarylthiazoles with NN-dialkylamine groups of different chain lengths. The UV/Vis absorption, photoluminescence, and electrochemical behavior were similar regardless of chain length, whereas liquid-crystalline behavior and thermal characteristics were found to be dependent on the alkyl-chain length. The compounds with NN-diethylamine or N-butyl-N-methyl groups showed a stable liquid-crystalline phase over a wide temperature range as well as higher stability to thermal decomposition.

DOI： 10.1002/asia.200600305

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Plastic films coated with crosslinked liquid-crystalline polymer (CLCP) layers containing azobenzene moieties (plastic/CLCP bilayer films) were prepared by thermal polymerization of mixtures of an azobenzene monomer and a crosslinker placed between a plastic film and a glass substrate. When the glass substrate was untreated, the obtained bilayer film bent slightly away from the UV light source when irradiated on the CLCP layer side. This bending direction was the same as that of a hybridly aligned CLCP film. When the glass substrate was coated with a rubbed polyimide to strengthen the homogeneous alignment of the azobenzene moieties of the CLCP surface layer, the obtained bilayer film bent toward the irradiation direction of the incident UV light. It was the same as a homogeneously aligned CLCP film and the degree of bending was larger than that of the untreated sample. This means that the photoinduced bending behavior of the plastic/CLCP bilayer films strongly depends on the alignment of the azobenzene moieties of the CLCP surface layer facing the incident light.

DOI： 10.1080/1559961070143042

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

An amphiphilic diblock liquid-crystalline copolymer consisting of poly(ethylene oxide) (PEO) and polymethacrylate containing an azobenzene moiety in the side chain was prepared by atom transfer radical polymerization (ATRP). The specifically-designed chemical constitution and the low molecular-weight polydispersity enable the block copolymer to form a regular microphase-separated nanostructure self-assembled in its bulk films, in which a hexagonal packing of the PEO cylinders normal to the substrates was dispersed in a continuous phase of azobenzene mesogens with out-of-plane alignment. Then a commerically available rubbing technique was first used to control the microphase-separated domains in the copolymer films, By introducing novel supramolecular cooperative motions between ordered azobenzene mesogens and PEO microphase domains, macroscopic array of PEO nanocylinders was regularlly formed along the rubbing direction. Both the clotted and parrallel stripe patterns of PEO nanocylinders were successfully obtained in the same block copolymer.

DOI： 10.1080/15421400701680812

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

A novel liquid-crystalline polymer (LCP) containing an azobenzene group directly connected to a tolane moiety (azotolane moiety) was synthesized. The LCP showed a nematic phase in a broad temperature range (>200 degrees C). Trans-cis photoisoinerization and cis-trans thermal isonterization occurred even though the LCP contains a long azotolane moiety. The homogeneously aligned film of the LCP exhibited an. extremely large value of Delta n (0. 70 at 633 nm). Upon irradiation with a pumping beam in the LC phase, a large change in An was induced due to destruction of the homogeneous alignment of the azotolane moieties.

DOI： 10.1080/15421400701680911

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A novel nickel complex ligated with 2-(2,6-diisopropylanilino)-1,4-naphthoquinone (1) was synthesized. The molecular structure of 1 determined by X-ray analysis was a square-planar geometry. Complex 1 conducted ethylene polymerization at 40 degrees C in a low activity to give linear polyethylene. On the other hand, 1 activated with 4 eq. of B (C(6)F(5))(3) was highly active for ethylene polymerization and gave a polymer possessing short chain branches of methyl, ethyl and propyl groups formed by a chain walking mechanism, as well as long chain branches, of which the content was almost the same as the total content of short chain branches. These results suggest that the macromonomer formed via beta-hydride elimination should have effectively copolymerized with ethylene to give the long chain branches in the B(C(6)F(5))(3)-activated system.

DOI： 10.1002/marc.200600335

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

SiO2-supported cocatalyst was prepared from trialkylaluminium-free modified methylaluminoxane. Propene polymerization was performed by [t-BuNSiMe2(Flu)]TiMe2 combined with the prepared cocatalyst in heptane. The supported system showed a comparable initial activity to the corresponding homogeneous system that conducts living polymerization of propene and gave the polymer with higher molecular weight and broader molecular weight distribution. Deactivation and chain transfer reaction however occurred in the supported system.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Input and output grating couplers with a grating period of 1.3 mu m were fabricated in an azobenzene liquid-crystalline polymer film by holography. When a He-Ne laser beam at 633 nm was incident to the input grating, the beam was coupled, propagated in the polymer film, and then was taken out from the output grating. The coupling efficiency of the input and output coupler was estimated as about 1.1% in TE mode. Upon irradiation of the film with UV light to cause trans-cis photoisomerization of the azobenzene moiety, the intensity of the output beam was repeatedly changed.

DOI： 10.1080/15421400600932603

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

A liquid-crystalline monomer containing an azobenzene moiety was synthesized and copolymerized with an acrylate monomer with a hydroxyl group. Crosslinked azobenzene liquid-crystaline polymer fibers were obtained by the following method. Firstly, the copolymer and 4,4′-methylenebis(phenyl isocyanate) as a crosslinker were mixed on a hot stage. Then the mixture was pulled into a fiber. The photoinduced bending behavior of the obtained fiber has been investigated. When the fiber was exposed to UV light, the fiber bent toward the irradiation direction. Then the bent fiber reverted to the initial state upon exposure to visible light.

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Language：English   Publishing type：Research paper (international conference proceedings)  

Molecular and supramolecular orderings have attracted much attention because of their potential applications in multidisciplinary fields of nanotechnology. At a molecular level, chromophore molecules such as azobenzenes (AZs) are well-known for photoinduced alignment with their transition moments almost perpendicular to the polarization of the actinic light by repetition of the trans-cis-trans isomerization cycles. On the other hand, supramolecular ordered nanostructures self-assembled in block copolymer films have been widely used as templates or scaffolds to prepare nanomaterials. In the microphase-separated processes, the supramolecular function between incompatible phases plays an important role in the formation of diverse nanostructures such as sphere, cylinder, double gyriod, double diamond and lamellae. Here we incorporate the photoresponsive AZs into block copolymers and transfer the photoinduced molecular ordering to the supramolecular level. Therefore, well-ordered nanostructures in the AZ-containing block copolymers might be obtained by the photocontrol method. In this paper, a bromo-terminated poly(ethylene oxide) (PEO) with 114 repeat units was used as a macroinitiator to prepare an AB-type diblock copolymer by a typical atom transfer radical polymerization (ATRP). The GPC curve gives a number-average molecular weight (Mn) of 34,000 and a narrow polydispersity index of 1.07 due to the living character of ATRP. The second block of AZ-containing poly(methacrylate) with a degree of polymerization of 60 was obtained from the 1H NMR spectrum. Two phase-transition peaks on heating appeared at 40.1 and 158.4°C in its thermogram by differential scanning calorimetry, corresponding to PEO melting point - smectic phase - isotropic phase, respectively. Upon annealing at 140°C, the PEO block self-assembled into nanocylinders with a diameter of about 7 nm dispersed in the AZ liquid-crystalline (LC) matrix with a periodicity of 15 nm. The Fast Fourier Transform (FFT) image indicated a hexagonal packing of the PEO cylinders perpendicular to the substrates. Then a linearly polarized laser beam at 488 nm was used to control nanocylinders self-assembled in an amphiphilic diblock liquid-crystalline copolymer. Under the function of the supramolecular cooperative motions between the ordered AZ LCs and the microphase separation, the alignment of the PEO nanocylinders is perpendicular to the polarization direction of the actinic light. By the simple and convenient way of photocontrol, the macroscopic parallel array of nanocylinders can be easily obtained in an arbitrary area. Furthermore, the non-contacted method might provide a novel opportunity to control the nanostructures even on curve surface.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Recently, there has been a considerable effort to develop artificial actuator materials that can mimic muscle performance. In this study, photoresposive behavior of crosslinked azobenzene liquid-crystalline polymer fibers was investigated. The fibers were prepared by pulling the mixture of a copolymer and a crosslinker. When the fiber was exposed to UV light, the fiber bent toward the irradiation direction. Then the bent fiber reverted to the initial state upon exposure to visible light. Moreover, bending directions could be controlled by changing the irradiation direction.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Crosslinked azobenzene liquid-crystalline polymer films with hybrid alignment were prepared by in-situ photopolymerization and their photoresponsive behavior was investigated. It was found that the films showed photoinduced bending and unbending behavior. The bending direction of the films was determined by surface alignment treatment. In addition, thermomechanical analysis was performed to measure mechanical force generated during the bending process.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

We have synthesized liquid-crystalline polymers (LCPs) containing a long mesogenic core in which an azobenzene group is directly connected to a tolane moiety (azotolane moiety). To evaluate birefringence of the homogeneously aligned polymer films, the LCP films were placed between a pair of crossed polarizers and the transmittance of a probe beam (633 nm) was carefully measured. Before irradiation with a pumping beam, the values of birefringence were extremely large (about 0.7). Upon irradiation with the pumping beam, the largest change in alignment of the azotolane moieties was observed in P5ATTA which contains two azobenzene moieties in the mesogen core.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Diblock copolymers were synthesized from azobenzene methacrylate and cyanobiphenyl methacrylate with a macroinitiator of poly(ethyleneoxide) (PEO) or poly(methyl methacrylate) (PMMA) by an atom transfer radical polymerization (ATRP) method. The copolymer with well-defined structures were prepared and showed phase-separated structures.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

We synthesized an azobenzene liquid-crystalline monomer and a monomer having a carboxylic acid as a hydrogen bond donor. Copolymer was prepared by radical polymerization of the two monomers. The thermal properties of the complexes are different from those of hydrogen bond donor and acceptor compounds. The thermal properties of the hydrogen-bonded complexes prepared from mixtures of the copolymer and bisazopyridine were evaluated by DSC and IR measurement. Bisazopyridine, capable of recognizing hydrogen bond donor molecules at the pyridyl ends, was selected as a hydrogen bond acceptor. The hydrogen-bonded films were prepared by dissolving sodium chloride plates. Photoresponsive behavior of the hydrogen-bonded film was investigated.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Polymer particles containing tolane moieties with a high birefringence were prepared by soap-free emulsion polymerization. When a reflection spectrum of the film of self-assembled polymer particles was measured, a Bragg diffraction peak due to the periodic structure was observed.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

A crosslinkable oligothiophene was synthesized, and the photoresponsive behavior of nematic liquid crystals doped with the crosslinkable dye molecule was investigated. The photoinduced diffraction rings were observed upon irradiation with an Ar+ laser beam at 488 nm. The reoriented liquid crystals were immobilized by irradiation with 366-nm light from a high-pressure Hg lamp.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

We synthesized novel azobenzene liquid-crystalline polymers with a thienylacetylene moiety, and examined their properties. We prepared homogeneously aligned films, and evaluated their order parameter and birefringence. We observed the formation of holographic gratings upon irradiation of two laser beams.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

[t-BuNSiMe2(2,7-t-Bu(2)Flu)]TiMe2 and [t-BuNSiMe2(3,6-t-Bu(2)Flu)]TiMe2 were synthesized and characterized by elemental analysis, H-1 NMR, and single-crystal X-ray analysis. These complexes were applied for propylene polymerization using dried modified methyaluminoxane (dMNIAO) as a cocatalyst at 0 and 25 degrees C. The introduction of tert-butyl substituents to the fluorenyl ligand improved the activity more than 3 times regardless of the position of the substituents. The postpolymerization testified that both catalytic systems conducted the propylene polymerization in a living manner at both 0 and 25 degrees C. The propagation rate increased linearly against the Al/Ti ratio from the range of 100-400 with keeping the number of polymer chains constant, which directly indicates that a larger amount of dMMAO enhanced the propagation rate. The introduction of tert-butyl substituents also improved the syndiospecificity: the 3,6-position was more effective than the 2,7-position, and [t-BuNSiMe2(3,6-t-Bu(2)Flu)]TiMe2 gave the living polypropylene with the syndiotactic triad of 0.93 and the melting point of 142 degrees C.

DOI： 10.1021/ma050898i

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The photoinduced change in refractive index of poly(methyl methacrylate) films doped with an azobenzene liquid crystal was measured by the prism-coupling method. Upon irradiation of the film with a high-pressure mercury lamp at 366 nm, the coupling angles shifted and then recovered to the initial position by turning off the light. The change in refractive index was found to be 2x10(-3), which is attributed to the reversible photoisomerization of the azobenzene moieties.

DOI： 10.1063/1.2076432

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

Three oxadiazole derivatives with an amine and an alkyl tail were designed and synthesized as novel photo- and electro-active materials: 2-(4'-propylbiphenyl-4-yl)-5-(4-N,N-dimethylaminophenyl-4-yl)-1,3,4,-oxadiazole (3-OXD-Me), 2- (4'-heptybiphenyl-4-yl)-5-(4-N,N-dimethylaminophenyl-4-yl)-1,3,4,-oxadiazole (7-OXD-Me), 2-(4'-heptylbiphenyl-4-yl)-5-(4-N,N-diphenylaminophenyl)-1,3,4,-oxadiazole (7-OXD-Ph). It was found that the length of an alkyl tail and the structure of an amine strongly affect the phase structure of the oxadiazole derivatives; 3-OXD-Me showed a crystalline phase, 7-OXD-Me showed a liquid-crystal line (LC; nematic) phase and 7-OXD-Ph exhibited a glassy amorphous state. All the compounds emitted strong blue fluorescence: the maximum wavelengths of emission were 420-436nm with high quantum yields (0.81-0.91). Furthermore, polarized photoluminescence was observed in 7-OXD-Me in a nematic phase, and the order parameter estimated by the polarized emission was 0.18. These compounds, therefore, are potential multifunctional materials for photo- and electio-active devices.

DOI： 10.1143/JJAP.44.485

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Optical switching of a 1.55-mu m laser beam was explored by means of photochemical phase transition of polymer and low-molecular-weight azobenzene liquid crystals (LCs). It was observed that the 1.55-mu m laser beam could be repeatedly switched by turning on and off the actinic light, and a large change in refractive index was induced in the azobenzene LCs at the near infrared region. It was also found that controlling the thickness of LCs could enhance the change in the transmittance of the 1.55-mu m laser.

DOI： 10.1080/154214091009707

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

A series of poly(alkyl methacrylate)s having azobenzene and cyanobiphenyl moieties were synthesized and their optical properties were characterized. The effect of content of the photosensitive unit and the length of alkyl chain of a transparent unit on the photoresponsive alignment behavior was investigated. The azobenzene monomer (photoresponsive unit), the cyanobiphenyl monomer (mesogenic unit), and the alkyl methacrylate monomers with methyl, ethyl, n-butyl, hexyl or lauryl group (transparent unit) were copolymerized to yield transparent polymer films. Upon irradiation of LPL at 488 nm, a uniaxial optical anisotropy was generated due to the molecular alignment. The photoinduced alignment behavior was strongly dependent on the alkyl chain length and the intensity of the actinic light.

DOI： 10.1080/15421400500253712

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The change in transmittance of a 1.55-mu m laser beam was investigated by a photochemical phase transition of an azobenzene liquid-crystalline polymer. Effects of the intensity of actinic light and temperature on the photoresponsive behavior were explored using laser beams at 633 nm and 1.55 mu m. It was found that the intensity of the actinic light or temperature affected on the response, regardless of the wavelength of the probe beam.

DOI： 10.1080/15421400500249017

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The photoresponsive behavior of an amphiphilic diblock liquid-crystalline (LC) copolymer (P40A37) was studied in both toluene solution and spin-coated film. The LC copolymer in a film state showed slower response and relaxation than that in the solution. Significant H-aggregation in the film led to a blue shift by 16 nm at the maximum absorption. The photochemical phase transition was observed with a polarizing optical microscope (POM) upon exposure to 366-nm light. The photoinduced isotropic state remained stable at room temperature, indicating the potential application for 2-D and 3-D storage.

DOI： 10.1080/15421400500253688

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Liquid-crystalline elastomers (LCEs) show both the elastic properties of rubbers and the anisotropy of liquid crystals. In this study, we synthesized a liquid-crystalline (LC) monomer with an azobenzene moiety and a flexible oxyethylene spacer. LCE films, which show low glass transition temperature, were prepared by thermal polymerization of the LC monomer and a cross-linker. The photoresponsive behavior of these LCE films were investigated. Because of high mobility of the oxyethylene spacer, the LCE films show low glass transition temperature and the lower stability in the alignment of mesogens even in the cross-linked structure.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Polarization grating was formed in azobenzene polymer films with thickness of 100 μm. Two beams from an Ar+ laser (488 nm) with different polarization combination were interfered in the film, and the light intensity of the first-order diffraction of a He-Ne laser beam (633 nm) was measured. The grating recorded with two s-polarized beams showed high diffraction efficiency (96 %) upon photoirradiation for 12 min. When two orthogonal circularly polarized beams were interfered in the film, the diffraction efficiency reached about 90 % within 3 min upon photoirradiation.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Extraordinary and ordinary refractive indices of a uniaxially aligned azobenzene liquid-crystalline polymer film was evaluated by a prism coupling method. Furthermore, the change in refractive index induced by photochemical phase transition was estimated.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

A liquid-crystalline monomer mixture was photopolymerized with interfered laser beams or a beam through a photomask at an Isotropic temperature. Optical anisotropy appeared only at the boundary between bright and dark areas. It is considered that liquid-crystalline monomers diffuse from the dark area to the bright area due to the consumption of monomers in the bright area, and the aligned monomers during diffusion processes are fixed by photopolymerization.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Polymer 1 bearing a 2,5-diarylthiazole moiety in the side chain was synthesized by radical polymerization with AIBN as an initiator. The obtained polymer 1 shows Mn of 13000 (Mw/Mn of 1.93). Measurements of DSC, UV-Vis spectrum, fluorescence spectrum, cyclic volutammetry, and liquid crystalline characteristics were also carried out.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

A liquid-crystalline monomer mixture was photopolymerized with interfered laser beams at isotropic temperatures. Molecular alignment parallel to the periodicity was observed in the wide region, while perpendicular alignment was obtained in the narrow region. On the other hand, the directions of molecular alignment were oblique at the boundaries between the wide and the narrow areas. Diffraction efficiency of the +1st and -1st order diffracted beams strongly depended on the handedness of the circularly polarized probe beam. It is assumed, therefore, that polarization gratings were formed by holographic photopolymerization of liquid-crystalline monomers.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Two-dimensional polymer periodic structures having cyanobiphenyl moieties and azobenzene moieties were fabricated by holographic photopolymerizarion, and their optical properties were investigated. Three beams through a grating mask from an Ar+ laser were interfered on a glass substrate coated with the mixture of monomers and a small amount of a photoinitiator. Photoirradiation was carried out at the light intensity of 3 mW/cm2 at 514.5 nm for 10 min and then unreacted monomers were removed with ethyl acetate. Observation of the obtained film with an atomic force microscope revealed that two-dimensionally periodic surface relief was created. When a probe beam from a He-Ne laser was incident to the film, six first-order diffractions appeared, and the intensity of the diffracted beams strongly depended on the polarization state of the probe beam.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Polarization gratings were formed in azobenzene-containing copolymer films with thickness of 100 μm. Two beams from an Ar+ laser (488 nm) with different combinations of polarization were interfered in the film at an incident angle of 7° with the total intensity of writing beams at 200 mW/cm2. The light intensity of the first-order diffraction of a He-Ne laser beam (633 nm) was measured with a photodetector. The grating recorded with two s-polarized beams showed high diffraction efficiency (96 %) upon photoirradiation for 13 min. On the other hand, the diffraction efficiency reached &gt
90 % within 13s upon photoirradiation with two orthogonal circularly polarized beams at 800 mW/cm2.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Polymer films containing an azobenzene moiety with a cyano group were prepared, and formation of gratings was explored. Two linearly polarized beams from an Ar+ laser (514 nm) were interfered in the film, and the light intensity of the first-order diffraction of a He-Ne laser beam (633 nm) was measured. The maximum diffraction efficiency rose up and reached 96 % upon photoirradiation at 100 mW/cm2 for 8 min. Furthermore, holographic multiple data storages which are characteristic of Bragg hologram were performed. The same spot of the film was irradiated with s- and p-polarized writing beams at different angles. When the recorded hologram was probed with the s-polarized reading beam, only one grating recorded with the s-polarized writing beams was detected preferentially. In contrary, the p-polarized reading beam recognized the other grating recorded with the p-polarized beams. It was clearly observed that the recorded hologram is not only angular dependent but also polarization dependent.

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

The authors found that anilinonaphthoquinone-ligated Ni complexes activated with 4 eq. of B(C6F5)3 showed high activity for polymerization of ethylene at 1 atm pressure. Polyethylenes produced by these catalytic systems at 40°C possessed the branched structure, while the linear structure was obtained at 0°C. The branched polyethylene had the short chain branches formed by chain walking via β-hydride elimination/reinsertion/migration and long chain branches. The contents of long chain-branches were almost the same with those of the short chain branches. It was assumed that the macromonomer formed via β-hydride elimination should effectively be copolymerizated with ethylene to give the long chain branches.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Ethene-norbornene (E-N) copolymerizations were carried out by (t-BuNSiMe(2)FIu)TiMe2 (1) and (t-BuNSiMe2C5Me4)TiMe2 (2) activated with methylaluminoxane (free from Me3Al) under an atmospheric pressure of ethene at 40 degreesC. 1 showed higher activity than 2. The activity of 1 increased with increasing the feed ratio of norbornene/ethene, but the opposite trend was observed for 2. In the same feed ratio (N/E = 8), the incorporation of norbornene was higher with 1 (N = 50 mol %) than with 2 (N = 38 mol %). The C-13 NMR spectrum of the E-N copolymer obtained with 1 was completely different from that with 2. The former showed the resonances of norbornene dyad and triad, whereas the latter showed only those of alternating and isolated norbornene structures. Some new signals were assigned to the rac,rac-NNN triad. The effects of activators and polymerization temperature were investigated with 1 in more detail, and the 1-Ph3CB(C6F5)(4)/Oct(3)Al system was found to show the highest activity at 80 degreesC and gave the E-N copolymer with the highest N content of 82 mol % and the glass transition temperature 237 degreesC.

DOI： 10.1021/ma048492d

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Controlling the optical properties of patterned optical materials is generally useful. Much headway has been made into patterning passive optical structures and fabricating them of a variety of materials. Recent efforts have been made to tune the properties thermally, electronically and optically. Liquid crystals offer several mechanisms for varying their optical properties. They have been incorporated into patterned templates to make electro-optic and photo-optic materials. Holographic photopolymerization provides a means to form an arbitrary structure incorporating multiple material phases such as liquid crystals. Electro optic holographic polymer dispersed liquid crystals (HPDLCs) have been the subject of extensive investigation. We report photo-optic HPDLCs incorporating azobenzene derived liquid crystals (Azo-LCs).

DOI： 10.1117/12.560014

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We have studied the nonlinear optical response of the nematic liquid crystal E7 doped with the oligothiophene dye TR5. Z-scan measurements showed a large positive (self-focusing) nonlinearity, originating in director reorientation. The oligothiophene dye enhances the nonlinearity of the host, in a similar manner to that of azo- and anthraquinone dyes in guest-host systems which exhibit the Janossy effect. The enhancement factor is unusually large
our TR5-E7 system showed as large a dye-induced optical torque enhancement factor as any observed in a guest-host system. Here we present our experimental results, determine the enhancement factor, and hypothesize that the dominant mechanism involves a photo-induced decrease in the orientational mobility of the dye molecules.

DOI： 10.1080/15421400490501581

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

In order to lower the operating voltage of molecularly doped electroluminescent (EL) devices using a low-molecular-weight liquid crystal (LC), we added a small amount of electrolytes (tetrabutylammonium bromide: TBAB) to the EL devices. The addition of TBAB decreased the driving voltages by one order of magnitude. Furthermore, the EL devices containing TBAB could be operated under not only a dc mode but also an ac mode.

DOI： 10.1143/JJAP.42.7366

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The additive effect of triphenylphosphine (Ph3P) was investigated in 1,3-butadiene polymerization with cobalt dichloride (COCl2) activated by methylaluminoxane (MAO); the catalytic system resulted in slowly-initiated living polymerization with a high cis-1,4 content (about 99%) at 0degreesC. The polymerization behavior, such as the relationship of polymer yield and number-average molecular weight ((M) over bar (n)) with polymerization time, was dependent on the amount of Ph3P added. In the presence of a small amount of Ph3P (Ph3P/Co = 0.025), the kinetic behavior qualitatively resembled that observed in the absence of Ph3P, which indicated that the catalytic system conducted slowly-initiated living polymerization. An increase in the amount of Ph3P (Ph3P/Co > 0.025), however, caused chain transfer reaction. The H-1 NMR analysis of the produced polymers showed that Ph3P changed the microtacticity from 99% of cis-1,4 to 88% of 1,2-unit, depending on the amount of Ph3P added. At the maximum amount of Ph3P (Ph3P/Co = 0.025) necessary for maintaining the livingness of the propagating species. 14% of the 1,2-inserted unit was incorporated at the expense of the cis-1,4-inserted unit. The addition of Ph3P (Ph3P/Co = 0.025) during the polymerization did not affect the livingness and gave a regio-block copolymer of 1,3-butadiene.

DOI： 10.1002/macp.200350052

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Electroluminescent (EL) behavior has been evaluated in a cell that contained molecular dispersion of 1,4-bis(N,N-diphenylaminophenyl-1,3,4-oxadiazolyl)benzene (OXD) in various liquid crystals (LC); 4-hexyloxy-4'-cyanobiphenyl, 4-octyloxy-4'-cyanobiphenyl (80CB) as low molecular-weight LCs and poly(8-(4-cyano-4'-biphenyl)-1-octanoylacrylate), poly (11-(4-cyano-4'-biphenyl)-1-undecanoylacrylate) as polymer LCs. Among the guest/host mixtures examined, the OXD/8OCB mixture showed the most stable LC phase even at the fraction of OXD up to 30 wt.%. EL emission was observed above the temperature where the OXD/8OCB mixture showed an LC phase. Furthermore, an EL device was fabricated that consisted of interdigital electrodes coated onto a glass substrate. It was found that the EL emission from the device was highly polarized. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0040-6090(03)00733-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Electrochemical and electroluminescent (EL) properties of a polymer liquid crystal (PLC) composed of an oxadiazole moiety as an electron-transporting unit and an amine moiety as a hole-transporting unit in the same side chain were investigated. It has been found that the polymer is a good candidate for a single-layer light-emitting diode (LED) because it combines carrier-transporting and emission properties in a single species. A polymer LED was fabricated with a simple configuration of ITO/PLC/MgAg to demonstrate EL behavior. The device showed the EL emission in a blue region with a maximum brightness of 13 cd/m(2) at 26 V. Furthermore, a polarized EL emission was observed due to self-assemblies of mesogenic chromophores. The dichroic ratio of the absorption of the polymer film determined by polarized absorption spectra measured with the polarized beam parallel and perpendicular to the rubbing direction was 1.8, and the dichroic ratio of the emission was estimated to be 1.6. These results clearly indicate that the origin of the polarized emission from the polymer film is the anisotropic arrangement of the mesogenic chromophores.

DOI： 10.1021/jp0215872

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

1,3-Butadiene polymerization was conducted at 0degreesC with cobalt dichloride (CoCl2) activated by different cocatalysts: MAO (methylaluminoxane), dried-MAO (substantially free of trimethylaluminum), MMAO (triisobutylaluminum-modified methylaluminoxane), dried-MMAO (substantially free of trialkylaluminum) and TMA (trimethylaluminum). MAO and MMAO were effective cocatalysts for 1,3-butadiene polymerization. CoCl2 activated with MAO showed slowly-initiated living polymerization which has been reported previously, whereas, that with MMAO showed deactivation. Neither dried-MAO nor dried-MMAO, TMA activated the catalyst, whereas dried-MAO-TMA (mixtures of dried-MAO and TMA) and dried-MMAO-TMA (mixtures of dried-MMAO and TMA) allowed the polymerization. These results indicated that trialkylaluminums were necessary with MAOs for generating the active species. Dried-MAO-TMA caused frequent chain transfer reactions, whereas dried-MMAO-TMA showed the living like polymerization not only with slow initiation but with slow propagation also, suggesting that the nature of the active species was strongly dependent on the structure of alkylaluminums and MAOs. The microstructure of the resulting polymers analyzed by H-1 and C-13 NMR was cis-1,4 (98-97%); the percentage slightly decreased in the following order: MAO > dried-MAO > MMAO > dried-MMAO, accompanied by the increase of trans-1,4 and 1,2-inserted units. (C) 2002 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We studied the formation of gratings by means of the photoinduced alignment change of polymer liquid crystals (PLCs) in a glassy state. To obtain high diffraction efficiency (eta), we prepared a novel PLC containing an azobenzene group directly connected with a tolane moiety (3AT) which has large birefringence (Deltan). It was found that the value of birefringence in 3AT was extremely high (Deltan = 0.39). When two s-polarized writing beams (Ar+ laser, 488 nm) were interfered on the surface of the 3AT film in the glassy state, multiple diffraction beams were observed immediately, resulting from the grating formation. We explored the effect of light intensity on the grating formation and the relation between the alignment change and eta. The value of eta showed a maximum when the change in photoinduced alignment was almost completed. Furthermore the value of eta was relatively high (eta = 20%) even though the alignment change of mesogens was small.

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The azobenzene liquid-crystalline gel (LCG) films with macroscopic uniaxial alignment were prepared to investigate photoresponsive behavior. By polarizing microscopy, fiber-like structures aligned in one direction were observed. Furthermore, with a confocal laser scanning microscope (CLSM), it was confirmed that the fiber-like structures were formed even in the bulk of the LCGs. When the LCG films were irradiated with UV light below Tg, changes in the microscopic surface morphology were observed, while no appreciable macroscopic change was observed. On the other hand, when the LCGs were plasticized by suspending in solvents or heating above Tg, the LCG films showed macroscopic changes (e.g. bending) upon UV light irradiation. The bending and unbending could be repeated just by changing the wavelength of the irradiation light. It was suggested that the bending is induced by an absorption gradient which produces a volume difference between the front surface area and the bulk of the gel films.

DOI： 10.1080/15421400390220827

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KODANSHA LTD  

Solid activators (S-MMAOs) were prepared by supporting dried modified methylaluminoxane (dried MMAO) on silica, alumina and magnesia. Propene polymerization was conducted at 0 degreesC by a chelating (diamide)dimethyltitanium complex ([ArN(CH2)(3)NAr]TiMe2, Ar = 2,6-Pr2C6H3) combined with S-MMAOs. These heterogeneous catalytic systems conducted the polymerization without any induction period. The number-average molecular weight (M-n) of the produced polymers increased linearly against the polymerization time accompanied by narrowing molecular weight distribution (M-w/M-n), which were slightly broader than that of the corresponding homogeneous system. Living polymerization of propene proceeded irrespective of the supports for dried MMAO. The propagation rate and the M-w/M-n value depended on S-MMAO employed. Among these catalytic systems, the [ArN(CH2)(3)NAr]TiMe2-dried MMAO/SiO2 system showed the highest propagation rate and the narrowest M-w/M-n value.

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DOI： 10.1021/ma025586j

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Polymer Preprints ACS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Inc.  

Electroluminescent (EL) emission has been investigated in a system which consisted of molecular dispersion of 1,4-bis(N,N-diphenylaminophenyl-1,3,4-oxadiazolyl)benzene (OXD) in a liquid crystal, 4-octyloxy-4'-cyanobiphenyl (80CB). EL emission was observed above the temperature where the OXD/80CB mixture exhibited a liquid-crystalline phase. In addition, we fabricated and evaluated emission of an EL device which consisted of interdigital electrodes coated onto a glass plate. © 2001 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint, a member of the Taylor &amp
Francis Group.

DOI： 10.1080/10587250108025289

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DOI： 10.1021/cm000358u

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A simple casting film of Poly(6-[4-(4-cyanophenyl)diazenylphenyl oxy] hexyl methacrylate)(PM6ABCN) was made on an untreated surface of a glass substrate and adopted as a typical sample to study photoinduced orientation of azobenzene liquid crystalline side chain homopolymers. Below Tg and after irradiation of light at 366 nm, 400 nm, and 436 nm, respectively, the sample shows different UV spectra which can give an expedition on the steady state of the photoinduced orientation. Under various conditions photoinduced orientation of PM6ABCN was examined, and results show that the orientation process is not only dependent on the light strength, but also on the temperature and the wavelength of polarized light used. The maximum extent of orientation below Tg can be obtained within 100 s under irradiation of polarized light of 20 mW/cm(2) at 400 nm, and irradiation at 366 nm causes a lower extent of orientation than that by irradiation at 400 nm and 436 nn because relative more cis isomer was produced in the steady state.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ACS  

Various donor-acceptor azobenzenes were synthesized, which contained alkoxyl or amino group or amino group as a donor and cyano group or nitro group as an acceptor. To reveal the effect of the donor and the acceptor, the photochemical phase transition behavior of the liquid crystals (LCs) in the guest-host system was examined. In the low-molecular-weight LC systems, 5CB was used as a host LC. In particular, the photochemical N-I and the thermal I-N phase transition behavior of LCs was determined.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HUTHIG & WEPF VERLAG  

The copolymerization of ethylene and a poly(propylene) macromonomer, the number-average polymerization degree (P-n) of which was about 11, was conducted with (tert-butanamide)dimethyl(tetramethyl-eta(5)-cyclopentadienyl)silanetitanium dichloride (CGC-Ti) combined with methylaluminoxane. The rate of ethylene consumption is increased by adding the macromonomer when copolymerization was carried out at 40 degrees C, whereas such rate enhancement could not be observed at 90 degrees C. It was found that the increase of ethylene polymerization rate is accompanied by the incorporation of the macromonomer. Based on differential scanning calorimetry (DSC) and C-13 NMR measurements of the produced polymers, it was proved that the poly(propylene) macromonomer was copolymerized with the present CGC-Ti catalyst and the P-n value of the macromonomer incorporated in the copolymer does not influence the conversion of the macromonomer.

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Switching behaviors of ferroelectric polymer liquid crystal (FPLC), poly(2-methylbutyl 4'-(10-acryloyloxydecyloxy)biphenyl-4-carboxylate), were successfully modulated reversibly by photochemical reaction of photochromic guests (azobenzene derivatives) doped in the FPLC. Chiral azobenzene (AB(chi)) possessing the same structure as the host FPLC at the chiral part was found to enhance the transmitted light intensity through a pair of crossed polarizers on the trans to cis photoisomerization, while the other achiral azobenzene derivatives reduced the transmitted light intensity on photoisomerization. This difference in photoresponsiveness has been attributed to the different effect of the trans-cis photoisomerization on the host mesogens, the change in molecular shape for the achiral azobenzenes and the change in dipole moment for AB(chi).

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Using a long-chain derivative of amino acid containing naphthalene, the arrangement of the chromophore in the LB films has been examined by circular dichroism (CD) together with UV absorption and fluorescence spectroscopies. The monolayer of N-stearoyl-L-lysyl-L-l-naphthylalanine methylester exhibits a transition from expanded to condensed states. For the LB films prepared at the surface pressures below and above the transition, polarized UV spectra suggest different orientations of the chromophore and also the CD spectra vary significantly of types and magnitude of a Cotton effect. These results were reflected in the fluorescence decay curves for the LB films. © 1992, Taylor &amp
Francis Group, LLC. All rights reserved.

DOI： 10.1080/10587259208047036

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.5360/membrane.7.203

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Polymer solutions and solids that contain light-sensitive molecules can undergo photo-contraction, whereby light energy is converted into mechanical energy. Here we show that a single film of a liquid-crystal network containing an azobenzene chromophore can be repeatedly and precisely bent along any chosen direction by using linearly polarized light. This striking photomechanical effect results from a photoselective volume contraction and may be useful in the development of high-speed actuators for microscale or nanoscale applications, for example in microrobots in medicine or optical microtweezers.

DOI： 10.1038/425145a

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Language：English   Publisher：AMER ASSOC ADVAN SCIENCE  

Liquid crystals are promising materials for optical switching and image storage because of their high resolution and sensitivity. Azobenzene liquid crystals (LCs) have been developed, in which azobenzene moieties play roles as both mesogens and photosensitive chromophores. Azobenzene LC films showed a nematic phase in trans isomers and no LC phase in cis isomers. Trans-cis photoisomerization of azobenzene with a laser pulse resulted in a nematic-to-isotropic phase transition with a rapid optical response of 200 microseconds.

DOI： 10.1126/science.268.5219.1873

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Liquid crystals are promising materials for optical switching and image storage because of their high resolution and sensitivity. Azobenzene liquid crystals (LCs) have been developed, in which azobenzene moieties play roles as both mesogens and photosensitive chromophores. Azobenzene LC films showed a nematic phase in trans isomers and no LC phase in cis isomers. Trans-cis photoisomerization of azobenzene with a laser pulse resulted in a nematic-to-isotropic phase transition with a rapid optical response of 200 microseconds.

DOI： 10.1126/science.268.5219.1873

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Language：English   Publisher：MACMILLAN MAGAZINES LTD  

LIQUID crystals have been used extensively as active media in display devices such as full-colour television screens. These devices are generally based on changes in the arrangement of the liquid-crystal molecules induced by electric fields, which change their optical properties1. Ferroelectric liquid crystals2,3 exhibit spontaneous polarization and therefore show a faster response to changes in the applied field. Switching of this field causes a reversal in the direction of polarization2-5. Here we report polarization switching in ferroelectric liquid crystals driven by a photochemical process. The liquid-crystal films are doped with a photochromic compound which undergoes trans-cis isomerization on irradiation. Photoisomerization induces a change in the switching potential of the host liquid-crystal film, and thereby causes switching at the irradiated sites. The process is fast, stable, reversible and repeatable, and should be exploitable in device applications.

DOI： 10.1038/361428a0

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LIQUID crystals have been used extensively as active media in display devices such as full-colour television screens. These devices are generally based on changes in the arrangement of the liquidcrystal molecules induced by electric fields, which change their optical properties1. Ferroelectric liquid crystals2,3 exhibit spontaneous polarization and therefore show a faster response to changes in the applied field. Switching of this field causes a reversal in the direction of polarization2-
5. Here we report polarization switching in ferroelectric liquid crystals driven by a photochemical process. The liquid-crystal films are doped with a photochromic compound which undergoes trans-cis isomerization on irradiation. Photoisomerization induces a change in the switching potential of the host liquid-crystal film, and thereby causes switching at the irradiated sites. The process is fast, stable, reversible and repeatable, and should be exploitable in device applications. © 1993 Nature Publishing Group.

DOI： 10.1038/361428a0

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

© 2018 Taylor & Francis Group, LLC. We prepared crosslinked azotolane liquid-crystalline polymer (LCP) films doped with a stilbene derivative (two-photon chromophore) utilizing an interpenetrating polymer network (IPN) structure. The IPN films bend toward the light source upon irradiation with femtosecond laser pulses at 600 nm, which can excite the stilbene derivative by two-photon absorption. The bending speed of the IPN films increases with the square of the laser pulse intensity, which is compelling evidence for the two-photon processes.

DOI： 10.1080/15421406.2018.1466241

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DOI： 10.1080/15421406.2016.1275724

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DOI： 10.1080/15421406.2017.1338462

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DOI： 10.1080/15421406.2015.1071981

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DOI： 10.1080/15421406.2015.1063923

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DOI： 10.1038/511300a

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Language：English   Publisher：ROYAL SOC CHEMISTRY  

Photo-induced molecular motion in a liquid crystal polymer film including azobenzene was studied by the heterodyne transient grating method. The film was confined in a liquid crystal cell, where it is a photomobile film under free-standing conditions. By observation of the refractive index change induced by a laser pulse, contraction of the film was observed on the order of several hundreds of nanoseconds, and the subsequent reorientation and molecular rotation dynamics were observed from a few microseconds to a hundred milliseconds. Finally, the cis isomer of azobenzene was thermally returned back to the trans isomer in about ten seconds because the film could not be bent in the liquid crystal cell. Since the contraction, reorientation and molecular rotation took place before the cis to trans back-transformation, these processes correspond to the preliminary molecular motion preceding the macroscopic bending of the film.

DOI： 10.1039/c4cp00457d

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：AMER CHEMICAL SOC  

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/adma.201100131

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Language：Japanese  

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Shortcoming of a planar self-emitting device is only a small fraction of light generated in the device available due to a total internal reflection at the air/substrate interface. To increase a luminance efficiency of the device, microlens arrays are most useful: they extract the total internal reflection of light at the air/substrate interface. In this study, we investigated photoinduced reorientation behavior of dye-doped polymerizable liquid crystals to fabricate a novel planar microlens array film as an optical component for a self-emitting device.

DOI： 10.1117/12.859779

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Language：Japanese  

CiNii Books

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Language：Japanese  

CiNii Books

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Language：Japanese  

An actuator is an energy transducer that can convert a variety of input energies to mechanical quantities such as displacement, strain, velocity and stress. Up to now, many types of materials have been developed as actuator materials. Polymer materials driven by light could play an important role as an efficient energy conversion system because light is an energy source that can be controlled remotely, instantly and precisely. Liquid-crystalline elastomers (LCEs) are superior soft materials that possess both LC orders and elasticity due to polymer networks. A large deformation can be generated in LCEs, such as reversible contraction and expansion, and even bending, by incorporating photochromic molecules, such as an azobenzene, with the aid of photochemical reactions of these chromophores. We summarize the recent progress of polymer materials that can convert light energy into mechanical work directly (photomechanical effect), especially photomobile polymers that show movements in all dimensions controlled by light. © 2009, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.66.79

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Language：Japanese  

An actuator is an energy transducer that can convert a variety of input energies to mechanical quantities such as displacement, strain, velocity and stress. Up to now, many types of materials have been developed as actuator materials. Polymer materials driven by light could play an important role as an efficient energy conversion system because light is an energy source that can be controlled remotely, instantly and precisely. Liquid-crystalline elastomers (LCEs) are superior soft materials that possess both LC orders and elasticity due to polymer networks. A large deformation can be generated in LCEs, such as reversible contraction and expansion, and even bending, by incorporating photochromic molecules, such as an azobenzene, with the aid of photochemical reactions of these chromophores. We summarize the recent progress of polymer materials that can convert light energy into mechanical work directly (photomechanical effect), especially photomobile polymers that show movements in all dimensions controlled by light. © 2009, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.66.79

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Amorphous copolymers were synthesized with azobenzene methacrylate, cyanobiphenyl methacrylate, and alkyl methacrylate, in which the azobenzene acts as a photoresponsive part to undergo photoisomerization, the cyanobiphenyl is involved in a change in refractive index triggered by the photoisomerization of the azobenzene, and the alkyl methacrylate is to prevent light scattering, respectively. The obtained polymers showed no LC phase in spite of the incorporation of the common mesogenic group. When two writing beams were interfered in the thick polymer films, the diffraction of the probe beam was observed. The first-order diffraction efficiency reached more than 70 % within 500 ms. On the other hand, the intensity of the zeroth-order beam decreased in proportion to the increase in that of the first-order diffracted beam. It is clear that the intensity of the zeroth-order beam is transferred to that of the first-order diffraction with no optical loss due to the formation of the Bragg gratings. When the writing beams were turned off, the diffraction efficiency remained unchanged. When the recorded grating was kept in the dark at room temperature, sufficient diffraction efficiency was generally retained after a year. However, the grating was easily erased when heated up above T-g for several seconds, and rewritability was confirmed more than 100 cycles. No shrinkage was observed through those processes.

DOI： 10.1117/12.828029

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

In this study, we irradiated homogeneously aligned films of an azotolane liquid-crystalline polymer with a single femtosecond (fs) laser pulse. Upon irradiation of the single pulse, the change in Delta n was induced by destruction of due to destroy the homogeneous alignment of the azotolane moieties was induced. The estimated value of the change in Delta n was >0.2, and the response time was about 400 ns. When the experiment temperature was below glass transition temperature, the change in alignment induced by the pulsed irradiation was preserved without a thermal relaxation. On the other hand, the changed alignment completely recovered to the initial state with an increase in temperature.

DOI： 10.1117/12.804146

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Language：English   Publisher：John Wiley & Sons, Inc.  

DOI： 10.1002/9780470439098

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Various kinds of crosslinked liquid-crystal line polymers were synthesized with acrylate monomers and diacrylate cross-linkers containing azobenzene moieties. The effect of spacer length on photoinduced bending behavior of the polymer films was investigated. The films with long spacers exhibited low glass transition temperatures and underwent bending and unbending behavior at room temperature. Mechanical force generated during the process of UV light irradiation was also measured. It was found that the maximum force increased with the increment of the cross-linking density and the intensity of UV light.

DOI： 10.1117/12.794183

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Language：English   Publisher：ROYAL SOC CHEMISTRY  

Freestanding crosslinked liquid-crystalline polymer films obtained by self-assembly through intermolecular hydrogen bonding showed photoinduced bending and unbending. The structural change at the microscopic level, caused by trans-cis photoisomerization of the azobenzene moieties at the hydrogen-bonded crosslinks, is successfully converted into a macroscopic deformation in the liquid-crystalline polymer films.

DOI： 10.1039/b715855f

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Language：English   Publisher：AMER CHEMICAL SOC  

Optically transparent thick films of methacrylate copolymer containing donor-acceptor-type azobenzene and cyanobiphenyl moieties were prepared, and their optical properties were explored in terms of a photoinduced change in molecular alignment and the formation of Bragg gratings with angular and polarization multiplicity. Azobenzene moieties substituted with ethoxy, cyano, and nitro groups were employed, and their photoresponsive behavior was investigated. It was found by polarized UV-vis spectroscopy that the alignment of azobenzene moieties in the films was random in the initial state but became perpendicular to the direction of polarization of the writing beam after irradiation with a linearly polarized beam from an Ar+ laser at 514 nm. The film containing the cyanoazobenzene moieties showed the fastest formation of optical anisotropy due to an efficient change in molecular alignment. When two linearly polarized beams from the Ar+ laser were allowed to interfere in the films with a thickness of 200 mu m, the diffraction beam was observed immediately and reached 97% upon photoirradiation at 200 mW/cm(2) for 5 min. It was clearly observed that the response time became shorter with an increase in the light intensity of the writing beams, maintaining the high diffraction efficiency. Furthermore, it was clearly seen that the diffraction efficiency strongly depended on the direction of polarization of the reading beam. Holographic multiple data storage in a film was demonstrated, and 55 holograms with angular multiplicity were recorded successfully. In addition, multiple data storage using the polarization and angle selectivity simultaneously was first demonstrated.

DOI： 10.1021/la061506j

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Language：English   Publisher：AMER CHEMICAL SOC  

Holographic gratings were formed in thick polymer films containing azobenzene and diphenylacetylene (tolane) moieties in the Bragg regime. Amorphous polymers containing various contents of the azobenzene moiety with photosensitivity and the tolane moiety with large birefringence in the side chain were synthesized, and optically transparent thick polymer films were prepared. The films were irradiated with a linearly polarized beam from an Ar+ laser (488 nm), and the transmittance of a He-Ne laser beam (633 nm) through a pair of crossed polarizers, with the film between them, was measured to estimate a photoinduced birefringence (Delta n). The value of Delta n increased with an increase in the tolane moiety content in the polymer films. When two linearly polarized beams at 488 nm were interfered in the film, a diffraction beam was observed, and the maximum diffraction efficiency (eta) increased with the tolane moiety content. In the film containing 70 mol% of the tolane moiety, the highest eta of 99% was achieved, and angular selectivity due to Bragg diffraction was clearly observed. We consider the cooperative molecular motion of the tolane moieties to be induced by the photoinduced change in alignment of the azobenzene moieties even if the polymers show no liquid-crystalline phase. When two orthogonal circularly polarized beams were allowed to interfere in the film, a Bragg-type polarization grating was formed. It was found that the value of eta reached 90% within 920 ms.

DOI： 10.1021/la061587j

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Language：Japanese   Publisher：新技術コミュニケ-ションズ  

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：ROYAL SOC CHEMISTRY  

The change in shape inducible in some photo-reversible molecules using light can effect powerful changes to a variety of properties of a host material. The most ubiquitous natural molecule for reversible shape change is the rhodopsin-retinal protein system that enables vision, and this is perhaps the quintessential reversible photo-switch. Perhaps the best artificial mimic of this strong photo-switching effect however, for reversibility, speed, and simplicity of incorporation, is azobenzene. This review focuses on the study and application of reversible changes in shape that can be achieved with various systems incorporating azobenzene. This photo-mechanical effect can be defined as the reversible change in shape inducible in some molecules by the adsorption of light, which results in a significant macroscopic mechanical deformation of the host material. Thus, it does not include simple thermal expansion effects, nor does it include reversible but non-mechanical photo- switching or photo-chemistry, nor any of the wide range of optical and electro-optical switching effects for which good reviews exist elsewhere.

DOI： 10.1039/b705619b

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200603053

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Novel liquid-crystalline polymers (LCPs) containing a long azotolane moiety were synthesized, and the relationship between the chemical structures and the photoresponsive behavior was investigated. All homogeneously aligned LCP films exhibited extremely high values of birefringence (Δn) in the wide wavelength range. Specifically, the azotolane LCP with two azobenzene units showed the most efficient change in the alignment of the azotolane moiety with a huge change in Δn (≥0.65). This means that the high value of Δn in the homogeneously aligned state can be converted to the change in Δn effectively. Copyright © 2006 American Chemical Society.

DOI： 10.1021/ja0664382

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

A convenient pathway for controlling defect-free nanoscopic domains large areas is illustrated. A simple rubbing technique is used to align nanocylinders self-assembled in an amphiphilic diblock liquid-crystalline copolymer by introducing novel supramolecular cooperative motions between mesogens and microphase domains. A 3D macroscopic array of the nanocylinders over a large area is achieved parallel to the rubbing direction (see figure and inside cover).

DOI： 10.1002/adma.200600582

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Language：English   Publisher：AMER INST PHYSICS  

A liquid-crystalline polymer in the side chain was synthesized through copolymerization of a bipolar carrier-transporting monomer with a liquid-crystalline monomer containing oxadiazole moieties substituted with trifluoromethyl groups. A single-layer light-emitting diode of indium tin oxide (ITO)/copolymer/MgAg emitted white light with a maximum luminous efficiency of 0.1 cd/A. The origin of the white emission in the copolymer is the electroplex between bipolar carrier-transporting moieties and strong electron-withdrawing moieties. Furthermore, a simple multilayer device with configuration of ITO/poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)/copolymer/MgAg device showed white emission with CIE 1931 chromaticity coordinates (x,y): (0.30, 0.33). (c) 2006 American Institute of Physics.

DOI： 10.1063/1.235610

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Language：English   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja064148f

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Language：English   Publisher：ELSEVIER SCIENCE SA  

One- and two-photon induced phase transition behavior of low-molecular-weight and polymer liquid crystals (M) was observed. When a photochemical reaction of a two-photon absorbing dye was induced in a nemnatic (N) LC, N-to-isotropic (I) phase transition was induced with high spatial resolution. As a result of the phase transition, the refractive index of the materials was changed by two-photon processes. Furthermore, the I phase induced in the polymer LC was thermally stable and it still appeared after heating above N-I phase transition temperature. The results reported here are the first observation of the photochemical phase transition of the LCs induced by a two-photon process. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2005.09.118

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Language：English   Publisher：ELSEVIER SCIENCE SA  

In order to lower the operating voltage of molecularly doped electroluminescent (EL) devices using a low-molecular-weight liquid crystal (LC), we added a small amount of electrolytes (tetrabutylammonium bromide: TBAB) to the EL devices. The addition of TBAB decreased the driving voltages by one order of magnitude. Furthermore, the EL devices containing TBAB could be operated under not only a dc mode but also an ac mode. It has become apparent that the emission intensity increases in the order of smectic A phase < nematic phase=isotropic phase, suggesting that the emission intensity is closely related to the viscosity of the LC phase and mobility of the electrolyte. (c) 2005 Elsevier B.V All rights reserved.

DOI： 10.1016/j.tsf.2005.07.003

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Synthesis of a highly birefringent liquid-crystalline polymer (LCP) containing the azotolane functional group in the mesogenic moiety was investigated. The homogeneously aligned film of the LCP film exhibited a large delta in a wide wavelength range. The photoismerization behavior of the azobenzene moiety in the mesogen in P4TA in toleune was investigated. Results show that the LCP film exhibits rewritability with little photobleaching.

DOI： 10.1002/adma.200501783

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Group 4 [η1:η3-tert- butyl(dimethylfluorenylsilyl)amido]dimethyl complexes [t-BuNSiMe2Flu]MMe2(M = Ti, 1; Zr, 2; Hf, 3) were synthesized in a one-pot synthesis starting from the ligand, MeLi and MCl4(M = Ti, Zr, Hf), respectively. The structures of these complexes were determined by X-ray crystallography and the results obtained revealed that the fluorenyl ligand coordinates to center metal in a η3-manner irrespective of center metal employed. Propylene polymerization was conducted at 0 or 20 °C in toluene by 1-3 combined with dried methylaluminoxane (MAO), which was prepared from the toluene solutions of MAO by removing free trialkylaluminiums, and HNMe2PhB(C6F5)4in the presence of triisobutylaluminium. The 1-dried MAO system gave the polymer with syndiotactic triad (rr) of 63% at 0 °C, whereas 2 and 3 did not give any polymer in the same conditions. The 2-dried MAO system gave the polymer with the highest syndiotacticity (rr = 97%) at 20 °C, although the activity was low. The 3-dried MAO system did not give any polymer even at 20 °C. When HNMe2PhB(C6F5)4was used in place of dried MAO at 20 °C, 1 gave almost atactic polymer, while 2 and 3 gave highly syndiotactic one (rr > 90%). These results indicate that the catalytic performance strongly depended on the center metal of the ansa- fluorenylamidodimethyl complexes as well as cocatalysts employed. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jorganchem.2005.08.027

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Language：English   Publisher：AMER CHEMICAL SOC  

Highly birefringent liquid-crystalline polymers (LCPs) containing an azobenzene group directly connected to a tolane moiety (azotolane moiety) were synthesized. Attention was focused on the effect of the position of the tolane moiety in the mesogenic azotolane group and the donor-acceptor substituent on photochemical phase transition behavior. In solution, cis-trans back-isomerization of the LCP containing azotolane moieties with a donor-acceptor was faster than that of LCPs having no acceptor groups. All the LCP films showed a homogeneous alignment and very high values of birefringence (about 0.4 at 633 nm). In the LCPs with a conventional azotolane moiety, a large change in birefringence (above 0.35) was induced repeatedly by irradiation of UV light. Furthermore, we investigated photoswitching behavior at telecommunication wavelength (1550 nm) based on the photochemical phase transition by irradiation of UV light.

DOI： 10.1021/ma0512814

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Holography is one of the most promising techniques that enables ultra-high density optical data storage with a simple and small optical setup. The key component in holographic devices is a holographic material that meets various requirements such as high diffraction efficiency, fast response, and stability. Furthermore, additional problems, rewritability and reversibility, must be solved in rewritable holographic materials which are more convenient. In this paper, we successfully achieved rewritable holograms with 55 multiplicities by a simple formulation of optically transparent copolymer films containing azobenzene and mesogenic moieties. The recorded hologram was stable for more than six months and was rewritable over 300 times. In addition, holograms with angle and polarization multiplicity were recorded by controlling the incident angle and the polarization direction of writing beams independently.

DOI： 10.1117/12.683484

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We have recently reported that amphiphilic diblock copolymers, which consist of PEO and azobenzene containing methacrylate form a highly ordered hexagonal-packed PEO cylinder structure in a nano-scale. We synthesized new amphiphilic diblock copolymer bearing a fluorescent 2,5-diarylthiazole moiety by ATRP with PEO-114BMP as an initiator. The obtained polymer shows Mn of 11,000-26,000 (Mw/Mn of 1.05-1.09). Measurement of UV-Vis and fluorescence spectra of the film of thus obtained diblock copolymer was also carried out before and after annealing.

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200601760

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200503684

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DOI： 10.1021/ma0512814

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DOI： 10.1063/1.2356101

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DOI： 10.1002/adma.200501783

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DOI： 10.1080/15421400600932603

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DOI： 10.1080/15421400600932603

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

Based on a hydrophilic poly(ethylene oxide) macroinitiator (PEOBr), a novel amphiphilic diblock copolymer PEO-block-poly(11-(4-cyanobiphenyloxy)undecyl) methacrylate) (PEO-b-PMA(11CB)) was prepared by atom transfer radical polymerization (ATRP) using CuCl/1,1,4,7,10,10-hexamethyltriethylenetriamine as a catalyst system. An azobenzene block of poly(11-[4-(4-butylphenylazo)phenoxyl]undecyl methacrylate) was then introduced into the copolymer sequence by a second ATRP to synthesize the corresponding triblock copolymer PEO-b-PMA(11CB)-b-PMA(11Az). Both of the amphiphilic block copolymers had well-defined structures and narrow molecular-weight distributions, and exhibited a smectic liquid-crystalline phase over a wide temperature range.

DOI： 10.1002/marc.200500498

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

CiNii Books

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

CiNii Books

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

CiNii Books

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

CiNii Books

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

CiNii Books

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

CiNii Books

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

CiNii Books

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Language：English   Publisher：WILEY-BLACKWELL  

DOI： 10.1002/adma.200500346

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

Starting in the 1960s, several kinds of photodeformable polymers have been developed, such as monolayers, polymer gels, solid films elastomers with different photodeformation mechanisms. This field evolved slowly until recently when significant achievements have been made. Most recently, Lendlein and co-morkers have put forward another new concept - using photo-crosslinking to prepare deformable polymers with various pre-determined shapes (Nature 2005, 434, 879). This highlight gives a general introduction into photodeformable polymers and brings forth future challenges.

DOI： 10.1002/macp.200500318

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Language：English   Publisher：AMER CHEMICAL SOC  

The photoinduced reorientation behavior of dye-doped nematic liquid crystals (LCs) was investigated. Thiophene derivatives with ester moieties were newly synthesized as the guest dye molecule. The liquid-crystalline behavior and optical properties of these compounds were evaluated, and the effect of the dye structure on the photoinduced reorientation behavior of the dye-doped LCs was investigated. The photoinduced formation of diffraction rings was observed as a result of the self-phase modulation effect at the intensity of 11 W/cm(2), when an Ar+ laser beam at 488 nm was irradiated above the threshold intensity. Comparison of the lowest threshold light intensity for the appearance of the diffraction rings revealed that the thiophene dye with ester moieties directly bound to the terminal thiophene shows a lower threshold intensity than those of any other dyes.

DOI： 10.1021/cm0503580

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Language：English   Publisher：AMER CHEMICAL SOC  

Steady-state and transient photocurrent measurements were carried out to study the charge carrier transport properties of polymer liquid crystal (LC) containing oxadiazole (OXD) and amine moieties in the same side chain. The steady-state photocurrent measurement with asymmetric electrodes of ITO and A1 and a short penetration depth of the illumination light indicated that both electrons and holes can be transported in this film. The transient hole photocurrent observed by time-of-flight (TOF) experiments was dispersive at room temperature. The hole drift mobility significantly depended on temperature and electric field and was determined to be 6.1 x 10(-8) cm(2)/Vs at a field of 9.1 x 10(5) V/cM. According to the disorder formalism, the Gaussian width of the density of states was determined to be 170 meV for holes. Despite the indication of possible electron transport in this film, we could not determine the electron mobility by TOF experiments due to strong dispersive photocurrent. We discuss the present charge transport properties of the film in relation to a large dipole attributed to an electrical push-pull structure of p-dimethylaminophenyl-substitited OXD moiety in polymer LC and its electroluminescent properties.

DOI： 10.1021/jp0453820

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Language：English   Publisher：ELSEVIER SCIENCE BV  

ansa-Indenylamidodimethyltitanium complex ([t-BuNSiMe(2)Ind]TiMe2:1) was synthesized by one-pot reactions starting from the ligand, MeLi and TiCl4. The structure of 1 was determined by X-ray crystallography and the results obtained revealed that the indenyl ligand coordinate to titanium in an eta(4)-tendency. Propylene polymerization was conducted with I in toluene or heptane as solvent at 0 degrees C in the presence of dried methylaluminoxane (MAO) or dried modified MAO (MMAO), which was prepared from the toluene solutions of MAO or MMAO by removing free trialkylaluminium contained. Polymerization behavior was investigated from the consumption rate of propylene in a semi-batch system. The dried MAO/toluene system showed the highest activity without any deactivation. The produced polymer in the dried MAO/toluene system had the highest molecular weight and narrowest molecular weight distribution. The number-average molecular weight of the polymer increased almost linearly with increasimg polymerization time accompanied by narrowing molecular weight distribution from 1.42 to 1.37 and the number of polymer chains was almost constant. Thus, it was found that quasi-living polymerization of propylene proceeded. The C-13 NMR measurement indicated that 1-dried MAO/toluene produced poly(propylene) with isotactic triad of 40%. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molcata.2004.12.035

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Language：English   Publisher：AMER CHEMICAL SOC  

Copolymerization of propene and norbornene (P-N) was conducted with (t-BuNSiMe2Flu)-TiMe2 (1) activated by Me3Al-free methylaluminoxane (dried MAO), modified methylaluminoxane (MMAO), and Ph3CB(C6F5)(4)/OCt(3)Al at 20degreesC under atmospheric pressure of propene. The 1-Ph3CB(C6F5)(4)/OCt(3)Al system showed the highest activity and gave the copolymer with the lowest molecular weight and broad molecular weight distribution. The 1-dried MAO system produced the copolymer with the narrowest molecular weight distribution. The detailed investigation of this system clarified that the norbornene content in the copolymer was almost proportional to the N/P feed ratio with a narrow polydispersity of 1.1-1.2 and the glass transition temperatures of the P-N copolymers increased linearly against the norbornene content in the copolymers, that is, 53degreesC with 17 mol % of norbornene and 249degreesC with 71 mol % of norbornene. The C-13 NMR spectra also suggested the random distribution of the comonomers in the copolymers obtained.

DOI： 10.1021/ma048117l

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DOI： 10.1080/154214091009932

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

Liquid-crystalline polymers containing an oxadiazole moiety as an electron-transporting unit and a carbazole moiety as a hole-transporting unit in the same side chain were designed and synthesized to investigate electroluminescent (EL) properties. The synthesized polymers showed high fluorescence quantum efficiency. Furthermore, it was found that the luminescent polymers possessed bipolar carrier-transporting property. The single-layer organic light-emitting diode was fabricated to demonstrate EL emission. The device, ITO glass/the polymer/MgAg, exhibited intense blue emission with a maximum brightness of 30 cd/m(2) at 30 V.

DOI： 10.1080/15421400500247318

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

Several kinds of symmetric and asymmetric phenylene-thienylene co-oligomers substituted with alkyl, alkoxy, ester or cyano groups in the ends were newly synthesized. Liquid-crystalline (LC) properties of these compounds were evaluated by differential scanning calorimetry and polarizing optical microscopy. It was found that all the compounds showed an LC phase. The photoinduced reorientation behavior of the dye-doped nematic LCs was investigated upon exposure to an Ar+ laser beam at 488 nm. The change in refractive index was estimated to be larger than 0.1. It was revealed that the dyes synthesized act as an efficient trigger for the photoinduced reorientation.

DOI： 10.1080/154214091009752

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Photoinduced bending and unbending behavior of cross-linked polymer films, prepared by in-situ polymerization of liquid-crystalline (LC) monomers with azobenzene moieties, is discussed. Various modes of bending have been achieved with various alignments of the photoactive mesogens in the elastomers. Exposure of a monodomain film to UV light to cause trans-cis isomerization of the azobenzene moieties leads to the bending of the film toward irradiation direction of the actinic light. Irradiation of a polydomain film with linearly polarized light results in the bending along the polarization direction of the light, which enables bending of the film along any direction. The LC alignment in the films significantly affected the photoinduced bending behavior.

DOI： 10.1117/12.622440

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To create polarized organic light emitting diodes (OLEDs), liquid-crystalline polymers (LCPs) containing oxadiazole and amine moieties in the side chain were design and synthesized. These LCPs emitted intense blue fluorescence with high quantum yield over 0.6 in a solution. Furthermore, polarized emissions of fluorescence were observed in a LC phase, and order parameters estimated by the polarized emission were about 0.2. They have proven to function as polarized blue-emitting materials for OLEDs.

DOI： 10.1117/12.620795

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DOI： 10.1021/jp0453820

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Language：English   Publisher：ROYAL SOC CHEMISTRY  

We have synthesized highly birefringent liquid-crystalline polymers (LCPs) containing an azobenzene group directly connected to a tolane moiety (P3ATm), in which the alkyl spacer length (CH2)(m) was varied as m 5 6, 9 and 12. All LCPs showed a nematic phase in a broad temperature range (> 170 degrees C). The homogeneously aligned LCP films showed a high value of birefringence ( about 0.4) and a large change in the birefringence could be induced by photoinduced alignment change. Grating formation of LCPs has been explored in a glassy state. The diffraction efficiency ( g) showed a maximum when an order-disorder change was completed in the bright areas of the interference patterns. Studies on the effects of light intensity on the grating formation suggested that the diffraction efficiency was high (eta = 20%) even though the alignment change of the azotolane moieties was small. Furthermore, the behavior of the grating formation was found to be dependent on the alkyl spacer length of P3ATm.

DOI： 10.1039/b506131h

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

Azobenzene liquid-crystalline elastomer (LCE) films with homeotropic alignment were prepared by in-situ photopolymerization of mixtures of an LC monomer and a cross linker, both of which contain azobenzene chromophores. Thermodynamic and mesomorphic properties of the monomers and the LCE films were determined by differential scanning calorimertry and polarizing optical microscopy. X-ray diffraction patterns revealed that the LCE films show a smectic A phase. Polarized UV spectra and conoscopic observation with a polarizing optical microscope demonstrated that the azobenzene mesogens are aligned homeotropically in the films.

DOI： 10.1080/15421400500205787

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

Cross-linked liquid-crystalline polymer films were prepared by polymerization of mixtures containing azobenzene monomers and cross-linkers with azobenzene moieties. Two types of the cross-linked liquid-crystalline polymer films were prepared: monodomain films and polydomains films. Photoirradiation of the monodomain films with UV linearly polarized light (LPL) gave rise to bending of the films toward actinic light along the polarization direction, when the light polarization was parallel to the rubbing direction. When the two directions were perpendicular to each other, the bending was isotropic without a preferential direction. On the other hand, exposure of the polydomain films to UV LPL led to bending of the films always along the polarization direction of the actinic light. This means that one can induce bending of the film along any direction precisely by choosing the polarization direction of the actinic light.

DOI： 10.1080/15421400590957215

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

We have synthesized two types of azobenzene liquid-crystalline polymers with a tolane moiety exhibiting high birefringence: one is the copolymer having an azobenzene moiety and a 3-ring tolane group in the side chain (PA-3T) and the other is the polymer containing a long mesogen core, in which the azobenzene group is directly connected to the tolane moiety (P3AT). The values of 0.35 and 0.39 in birefringence were obtained in PA-3T and MAT, respectively. When the film was irradiated with a writing beam at 488 nm, the change in birefringence was efficiently induced with P3AT compared with PA-3T.

DOI： 10.1080/154214091009932

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DOI： 10.1080/154214091009707

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DOI： 10.1080/15421400500253712

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DOI： 10.1080/15421400500249017

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DOI： 10.1080/15421400500249017

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DOI： 10.1080/15421400500253712

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DOI： 10.1080/154214091009707

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DOI： 10.1080/15421400500253688

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DOI： 10.1080/15421400500253688

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Language：English  

Four coumarin (2-oxo-2H-1-benzopyran) containing liquid crystalline polymethacrylates possessing the same monomer formula but different linkage directions and/or construction directions of their mesogens into the same main-chain were prepared and investigated. Each of the four polymers exhibits a smectic A liquid crystalline phase. The change of construction and/or linkage directions significantly affected their liquid crystalline properties. Especially, the change of the construction directions of the mesogens caused different photophysical and photochemical properties.

DOI： 10.1039/b408554j

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：ELSEVIER SCIENCE BV  

Recent progress in alignment modulation of azobenzene-containing liquid crystal systems by photochemical reactions has been reviewed by dividing the modulation methods into two types: phase transitions (order-disorder change) and change of liquid crystal directors (order-order change). First, photochemical phase transitions and alignment changes of liquid crystals in guest/host mixtures and polymers are summarized. Then, alignment control of liquid crystals by linearly polarized light and photoactive surface layers is discussed. Finally, recent applications of alignment change and photochemical phase transitions of liquid crystals in holographic technology and photomechanical effects are introduced. In addition, future possible applications for a variety of practical devices, such as display devices, optical switching and reversible optical image storage, are mentioned. (C) 2004 Japanese Photochemistry Association. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jphotochemrev.2004.10.004

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

A mesogenic compound (1) with a syw-chiral carbonate moiety was synthesized. The self-assembly process of the azobenzene LC with a simple structure without hydrogen bonds or stacking of cholesterol was investigated. 1 shows excellent gelation properties for various organic solvents. The gelation ability of the compound is due to the formation of one-dimensional fibrous structures. The fibrous self-assembled structure was formed by the ribbon-like aggregation of 1 through the dipole-dipole interactions of the chiral carbonate moieties. Furthermore, the photoresponsive behavior of physicalorganogels formed by the azobenzene gelator was investigated.

CiNii Books

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

We designed and synthesized novel liquid-crystalline (LC) materials containing an oxadiazole moiety as an electron-transporting unit and an amine moiety as a hole-transporting unit in a single unit. The most significant characteristic of the LCs is to possess bipolar carrier-transporting abilities. Electroluminescent (EL) devices were fabricated with a simple configuration of ITO/LC/MgAg to demonstrate EL behavior. Furthermore, the polarized EL was observed due to self-assemblies of mesogenic chromophores. Especially we found that a rubbed semi-conducting polymer layer acts not only as a hole-injecting layer but also as an LC alignment layer.

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Language：English   Publisher：AMER CHEMICAL SOC  

Received March 18, 2004; Revised Manuscript Received July 22, 2004 Norbornene polymerization via "vinyl addition" proceeded with (t-BuNSiMe(2)Flu)TiMe(2) (1) in the presence of various cocatalysts [methylaluminoxane (MAO), modified methylaluminoxane (MMAO), and Ph(3)CB(C(6)F(5))(4)/Oct(3)Al] at wide range of temperatures (20-80degreesC) with high activity. The 1-Ph(3)CB-(C(6)F(5))(4)/Oct(3)Al system produced 4.8 x 10(3) kg of polymer per mole of Ti per hour at 20degreesC. All the catalyst systems produced high molecular weight (M(n)) polymers. In the 1-MMAO system the yield and M values increased linearly keeping narrow molecular weight distribution against the Al/Ti ratio, suggesting that MMAO should take part not only in the initiation but also in the propagation reaction. The rate enhancement with higher Al/Ti ratio was also observed in the Ph(3)CB(C(6)F(5))(4)/Oct(3)Al system. The activity of the 1-dried MAO and 1-MMAO systems increased with raising reaction temperature up to 60degreesC, whereas that of 1-Ph(3)CB(C(6)F(5))(4)/Oct(3)Al decreased. The polynorbornenes obtained with 1 were amorphous, soluble in halogenated aromatic solvents, and stable up to 420degreesC. The film of polynorbornene prepared by solvent casting was highly transparent in the UV-vis region.

DOI： 10.1021/ma049455p

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

Homeotropically aligned azobenzene liquid-crystalline elastomer (LCE) films were prepared and investigated in terms of the photoinduced bending behavior. Upon irradiation of UV light which induces photoisomerization of the azobebzene moieties, the film bent away from the UV light and reverted to the initial state when irradiated at visible light, contrary to the bending behavior of a homogeneous film. This can be explained by a different volume transformation.

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

Photopolymerization of ferroelectric liquid-crystalline monomers was carried out under an electric field. Upon photoirradiation of an Ar^+ laser beam at 488 nm, a monomer mixture in a 2-μm cell was polymerized and the initial molecular alignment was stabilized. Next, two beams at 488 nm were interfered in the cell, and the light intensity of the first-order diffraction light of a He-Ne laser beam at 633 nm was measured. The diffracted light appeared due to the grating formation. By applying an electric field, the intensity of the diffraction light increased, indicating a change in alignment of the unreacted monomers.

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

Polymer azobenzene films containing various contents of a tolane moiety with large birefringence were prepared. Two linearly polarized beams of an Ar^+ laser (488 nm) were interfered in the film, and the light intensity of the first-order diffraction of a He-Ne laser beam (633 nm) was measured. In the film with thickness of 100 μm, the diffraction efficiency reached 99.2% when photoirradiation was performed at 200 mW/cm^2 for 13 min. The maximum diffraction efficiency was significantly influenced by the content of the tolane moiety.

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

Polymer films containing a donor-accepter type azobenzene moiety were prepared and formation of gratings based on a photoinduced change in refractive index was explored. When two linearly polarized beams of an Ar^+ laser (514 nm) were interfered in the CB30AB5 film (film thickness : 250 μm), the diffraction beam based on Bragg diffraction appeared immediately. The maximum diffraction efficiency reached 98% upon photoirradiation at 100 mW/cm^2 for 6 min. It was clearly observed that the response time became shorter with an increase in the light intensity of the writing beams, maintaining the high diffraction efficiency. Furthermore, holographic multiple data storages in the CB30AB5 film were demonstrated.

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

A flexible liquid crystal hologram was prepared as a novel type of holographic materials. Polycarbonate films covered with a polyimide were employed as a substrate, and toluene solution of a polymer azobenzene liquid crystal (PALC) was coated on the rubbed substrate, resulting in a flexible PALC film. We attempted the formation of gratings and holographic image storage of 3-D objects into the flexible film. A clear and bright 3-D image was successfully reconstructed even in the bent film. This indicates that the holographic diffraction grating is formed in the flexible PALC film.

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

Photonic crystal structures were formed by polymer particles containing azobenzene moieties and their optical responsiveness was investigated. A Bragg diffraction peak due to the periodic structure was observed in the PME3-30 film in the reflection spectrum. A change in the intensity of the diffraction peak was induced by irradiation of a linearly polarized beam at 488 nm. The observation of the film by SEM revealed the adhesion of the polymer particles induced by photoirradiation.

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Language：English   Publisher：WILEY-BLACKWELL  

One-dimensional holographic photonic crystals that incorporate photochromic azobenzene-derived liquid crystals azobenzene-derived liquid crystals (LCs) have been produced. The additive photochromic molecules disrupt the host LC nematic order, inducing an isothermal phase transition and changing the effective dielectric properties of the LC layer (see Figure). This imparts photo-optic properties to the structure, allowing for its reflectivity to be modulated with exposure to light.

DOI： 10.1002/adma.200400206

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Language：English   Publisher：INT UNION PURE APPLIED CHEMISTRY  

Liquid-crystalline gels and elastomers were prepared by polymerization of mixtures containing azobenzene monomers and cross linkers with azobenzene moieties. Oriented liquid-crystalline gels and elastomer films were found to undergo anisotropic bending and unbending behavior only along the rubbing direction, when exposed to alternate irradiation of unpolarized UV and visible light. In the case of polydomain liquid-crystalline elastomer films, the bending and unbending were induced exactly along the polarization direction of incident linearly polarized light. By altering the polarization direction of light, a single film could be bent repeatedly and precisely along any chosen direction.

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

Ethene-norbornene copolymerizations were conducted by (tBuNMe(2)SiFlu)TiMe2 (1) activated with dried methylaluminoxane (MAO) (free from Me3Al) at 0 degreesC and 20 degreesC under atmospheric pressure of ethene at various norbornene concentrations. At 0 degreesC and high norbornene concentration, the molecular weight of the copolymer increased linearly against polymerization time while keeping narrow molecular-weight distribution. The C-13 NMR spectrum revealed that random copolymer with 53 mol-% of norbornene was obtained. The glass transition temperature was above 150 degreesC.

DOI： 10.1002/masy.200450913

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Language：English   Publisher：AMER CHEMICAL SOC  

Syntheses of differently substituted 2,5-diarylthiophenes and 2,5-diarylthiazoles are carried out with the palladium-catalyzed C-H substitution reaction using AgF as an activator. Remarkably strong photoluminescence is observed in 2,5-diarylthiophene. Differences between the physical properties of liquid crystalline characteristics and cyclic voltammograms of thiophene and thiazole are also studied.

DOI： 10.1021/ol049386z

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

Propylene polymerization was conducted at 0degreesC in heptane or chlorobenzene (CB) by an ansa-fluorenylami-dodimethyltitanium complex combined with dried, modified methylaluminoxane that had been treated by dilution with heptane and successively repeatedly vacuum dried to remove any free trialkylaluminiums. The post-polymerizations testified that the living polymerization proceeded irrespective of the solvent used. The heptane system gave the syndiotactic poly(proplene)s (PPs). whereas the CB system gave almost atactic PPs. After the first polymerizations in heptane had been completed, the same amounts of propylene and CB were added for the second polymerization. This procedure gave the sydiotactic stereoblock PP with narrow molecular-weight distributions.

DOI： 10.1002/marc.200400032

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：SOC SYNTHETIC ORGANIC CHEM JPN  

Several kinds of photodeformable polymer systems containing azobenzenes, capable of generating photomechanical effects, are reviewed. In polymer amorphous systems including monolayers, gels and solid films, trans-cis photoisomerization of the azobenzene moieties accompanied by geometrical and dipolar changes caused contraction and expansion of the systems. Recently, polymer liquid-crystalline elastomers containing azobenzenes, a novel system able to produce the photomechanical effects, have been developed to achieve fast and large photoinduced deformations. It is interesting that not only photoinduced contraction but also photoinduced bending have been achieved. These deformations are ascribed to the subtle variation in microscopic ordering during the photochemical phase transition of the polymer liquid-crystalline elastomers. This new photomechanical system is potential for application in driving micromachines and nanomachines without the aid of batteries, motors and gears.

DOI： 10.5059/yukigoseikyokaishi.62.471

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Language：English   Publisher：AMER CHEMICAL SOC  

Oriented liquid-crystalline network films with various cross-linking densities were prepared by polymerization of mixtures of mono- and diacrylates, both of which contain azobenzene chromophores. The optical anisotropy in the films was evaluated by polarizing optical microscopy and polarized IR spectroscopy. The dichroic ratios and the order parameters of the films were estimated from polarized UV absorbance. The free-standing films were found to show photoinduced bending and unbending behavior upon alternate exposure to unpolarized UV light at 366 nm and unpolarized visible light at > 540 nm. It was observed that the films with different cross-linking densities exhibited different bending extents and speeds.

DOI： 10.1021/cm035092g

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

Batchwise polymerization of propylene was conducted at 0degreesC in heptane using [tert-BuNSiMe(2)Flu]- TiMe2 (1) combined with dried methylaluminoxane (MAO) and dried modified methylaluminoxane (MMAO), which were prepared from the toluene solutions of MAO and MMAO by removing the solvent and the free trialkylaluminium. The dried MMAO system quantitatively gave the polymer with higher molecular weight and narrower molecular weight distribution (MWD), ca. 1.3, compared with the dried MAO system. In addition, the polymerization with dried MMAO in toluene, chlorobenzene (CB) and ortho-dichlorobenzene (o-DCB), as solvent, also produced polymers quantitatively with MWD of ca. 1.1-1.3. The number average molecular weight ((M) over bar (n)) of the polymers, obtained with these systems, increased linearly against the polymer yield, while the narrow MWD was retained and the number of polymer chains was almost constant. The results of post-polymerization in heptane and o-DCB proved that the living polymerization proceeded irrespective of the solvent used. The semi-batch polymerizations under an atmospheric pressure of propylene indicated that the propagation rate was more than 10 times higher in o-DCB than in heptane. The C-13 NMR analysis of the polymers indicated that the syndiotacticity also depended on the polarity of the solvent and increased in the following order: CBless than or equal to o-DCB < toluene < heptane.

DOI： 10.1002/macp.200300137

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

Modified methylaluminoxane (MMAO), from which free AlMe3 and Al(iBu)(3) were reduced to ca. 0.1 mol-%, was supported on metal oxides, such as anhydrous silica gel, alumina, or magnesia; the metal oxide-supported MMAO prepared were used as a cocatalysts for propylene polymerization combined with a chelating (diamide) dimethyltitanium complex. The systems conducted living polymerization of propylene at 0degreesC regardless of the support for MMAO. The propagation rate constants (k(p)) of these systems and the molecular weight distribution ((M) over bar (w)/(M) over bar (n)) of the produced polymer depended on the metal oxide employed. The XPS analysis of the supported MMAOs suggested that the k(p) value increased with the Lewis acidity of MMAO on the support and the broadening (M) over bar (w)/(M) over bar (n) was ascribed to the distribution of k(p) caused by the heterogeneity of the supported cocatalyst.

DOI： 10.1002/macp.200350079

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Language：English   Publisher：ROYAL SOC CHEMISTRY  

Four coumarin (2-oxo-2H-1-benzopyran) containing liquid crystalline polymethacrylates possessing the same monomer formula but different linkage directions and/or construction directions of their mesogens into the same main-chain were prepared and investigated. Each of the four polymers exhibits a smectic A liquid crystalline phase. The change of construction and/or linkage directions significantly affected their liquid crystalline properties. Especially, the change of the construction directions of the mesogens caused different photophysical and photochemical properties.

DOI： 10.1039/b408554j

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Language：Japanese   Publisher：The Society of Polymer Science, Japan  

DOI： 10.1295/kobunshi.53.276

CiNii Books

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Other Link： https://jlc.jst.go.jp/DN/JALC/00237378453?from=CiNii

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Photoinduced bending and unbending behavior of liquid-crystal line elastomers is discussed. Various modes of bending have been achieved with various alignments of the photoactive mesogens in the elastomers: oriented Liquid-crystalline elastomer films were found to undergo anisotropic bending and unbending behavior only along the rubbing direction, when exposed to alternate irradiation of unpolarized UV and visible light; in the case of polydomain Liquid-crystalline elastomer films, a single film could be bent repeatedly and precisely along any chosen direction by using linearly polarized light.

DOI： 10.1117/12.562627

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Language：Japanese   Publisher：シーエムシー出版  

CiNii Books

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Language：English   Publisher：AMER INST PHYSICS  

Electroluminescent (EL) properties of a low-molecular-weight liquid crystal (LC), which is composed of an oxadiazole moiety as an electron-transporting unit and an amine moiety as a hole-transporting unit, were investigated. The most significant characteristic of the LC is to possess bipolar carrier-transporting abilities. The bipolar LC makes it possible to fabricate a simple EL device. We fabricated an EL device (cell gap: 2 mum) with configuration of indium tin oxide (ITO)/LC/MgAg. The device emitted visible light at above 10 V. In particular, the values of luminance and current density of an EL device containing poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT) as a hole-injecting layer were ten and six times higher than those of the ITO/LC/MgAg device without the PEDOT layer, respectively. Furthermore, surfaces of the glass substrate with an ITO electrode and a PEDOT layer were rubbed to align mesogens. Dichroic ratio of the emission from an ITO/rubbed PEDOT/LC/MgAg device was estimated to be 2.8. These results indicate that the origin of polarized emission in the LC phase is the anisotropic arrangement of the mesogenic units. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1621726

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Language：English   Publisher：AMER CHEMICAL SOC  

A new class of photo- and electroactive polymer materials showing an liquid-crystalline (LC) phase were designed and synthesized: four kinds of polymers with both oxadiazole and arylamine moieties as carrier-transporting groups in the side chain. Among them, the polymers with a dimethylamine and a methylcarbazole moiety show LC phases. Furthermore, all the polymers emitted strong blue fluorescence, and their fluorescent quantum yields were over 0.6. The aligned sample of the polymer with the carbazole moiety emitted polarized fluorescence at room temperature. One-layer type electroluminescent (EL) devices were fabricated by using the polymer with a triphenylamine moiety, which exhibited the highest quantum yield (similar to0.82), and found to emit the EL emission at blue region.

DOI： 10.1021/ma021406u

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Language：English   Publisher：ELSEVIER SCIENCE SA  

In order to improve the electro-optic properties of polymer stabilized ferroelectric liquid crystal display(PS-FLCD) cells, new functional monomer was synthesized. The PS-FLCD cells were fabricated by UV irradiation with varying monomer doping concentrations. The electro-optic Properties were with examined with respect to cell morphology of cell and response time.

DOI： 10.1016/S0379-6779(02)01107-4

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Language：English   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja0269189

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Language：English   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ma020958+

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Language：English   Publisher：ROYAL SOC CHEMISTRY  

The alignment direction of liquid crystals on polyimide alignment films prepared by in situ exposure to linearly polarized light (LPL) during thermal imidization of poly(amic acid)s has been found to be parallel to the direction of polarization of the LPL, whereas the conventional method, in which the alignment layers are exposed to LPL after imidization, leads to alignment perpendicular to the direction of polarization of the LPL.

DOI： 10.1039/b211689h

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

Unique characteristics were observed in phase-type gratings which were formed in polymer liquid crystal (PLC) films. We have investigated the formation and the properties of the holographic gratings recorded in PLCs with azobenzene moieties (photoresponsive unit). Two types of PLCs were examined: homopolymers of azobenzene monomers (PALC) and copolymers with a tolane moiety (mesogenic unit with a high birefringence) in the side chain. The diffraction efficiency (it) was enhanced in the LC phase. We obtained the value of eta of 31% while it was less than 1% in a glassy state in the Raman-Nath regime. This difference may be due to the modulation of refractive index (Deltan) based on alignment change of rnesogens in the PLC film. In addition, we attempted the holographic image storage of three-dimensional (3-D) objects in the PLC film. The 3-D object was reconstructed with high resolution (>5, 000 lines /mm).

DOI： 10.1080/115421400390243165

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DOI： 10.1021/ja0289189

PubMed

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Language：English  

Unique characteristics were observed in phase-type gratings which were formed in polymer liquid crystal (PLC) films. We have investigated the formation and the properties of the holographic gratings recorded in PLCs with azobenzene moieties (photoresponsive unit). Two types of PLCs were examined: homopolymers of azobenzene monomers (PALC) and copolymers with a tolane moiety (mesogenic unit with a high birefringence) in the side chain. The diffraction efficiency (η) was enhanced in the LCphase. We obtained the value of η of 31% while it was less than 1% in a glassy state in the Raman-Nath regime. This difference may be due to the modulation of refractive index (Δn) based on alignment change of mesogens in the PLC film. In addition, we attempted the holographic image storage of three-dimensional (3-D) objects in the PLC film. The 3-D object was reconstructed with high resolution (&gt
5,000 lines/mm).

DOI： 10.1080/15421400390243165

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DOI： 10.1021/jp0215872

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