川月 喜弘

A polymethacrylate copolymer comprised of light-emissive cyano-substituted dihexylfluorenevinylene (CN-DHFV) side groups and photo-cross-linkable 4-(4-methoxycinnamoyloxy)biphenyl (MCB) mesogenic side groups was synthesized and characterized. Irradiating a thin copolymer film with linearly polarized ultraviolet (LPUV) light and subsequent annealing generated a cooperative molecular reorientation of both side groups parallel to the polarization (E) of LPUV light. The resulting reoriented film showed a polarized light emission of the CN-DHFV groups with a polarization ratio of 5.6.

Liquid crystalline (LC) polymethacrylates with hexamethylene spacer groups terminated with photoreactive hydrogen (H) bonded 4-oxycinnamic acid (CA) in the side chain were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The influence of the molecular weight on the thermal property, photoreactivity, and thermally enhanced photoinduced molecular reorientation behavior was investigated. All polymers exhibited a nematic LC phase, and thermally enhanced photoinduced in-plane molecular reorientation was achieved by irradiating with linearly polarized UV light and subsequent annealing. The molecular weight did not affect the photoreactivity and the axis-selectivity of anisotropic photoreaction of thin films, but effective annealing temperature and the maximum thermally enhanced in-plane order decreased as the molecular weight of the polymer decreased.

The diffraction properties of polarization holographic gratings fabricated using the orthogonally elliptical polarized light have been systematically investigated on the basis of the Jones calculus. The theoretical prediction based on the Jones calculus was experimentally confirmed to be valid by fabricating the polarization holographic gratings in azobenzene-containing amorphous polymer films. The ellipticity of the diffraction beam was well-controlled by varying the ellipticities of the writing beams. The diffraction properties were well explained by the Jones calculus. © 2010 The Japan Society of Applied Physics.

New photo-cross-linkable liquid crystalline polymethacrylate with 4-methoxybistolane side groups was synthesized and its thermally enhanced photoinduced molecular reorientation behavior was investigated using a linearly polarized (LP) UV light. Since the bistolane mesogenic side groups were axis-selectively photoreacted under irradiating with LPUV light, annealing procedure generated the thermally enhanced molecular reorientation parallel to the polarization (E) of LP-365 nm light. The axis-selectively photoreacted bistolane moieties acted as the photo-cross-linked anchor to reorient non-photoreacted side groups along them, which direction was parallel to E. The maximum generated in-plane order parameter and birefringence were 0.43 and 0.18, respectively. The influences of degree of the photoreaction and the annealing temperature on the molecular reorientation behavior were investigated in detail. Furthermore, polarization holography using 325 nm He-Cd laser was carried out to fabricate pure polarization gratings with various polarization of the light source. © 2010 CPST.

Patterned polarized blue-light emission was achieved using a new liquid-crystalline fluorene derivative (F1) on a patterned photoalignment layer. Adjusting the doses of linearly polarized (LP) UV light exposure onto the photoalignment layer controlled the alignment direction of F1, which coincided with the molecular reorientation direction of the photoalignment layer. An electroluminescent device with orthogonally patterned molecular orientation was fabricated, demonstrating patterned polarized blue-light emission with a polarization ratio between 2.7 and 3.5. © 2009 The Japan Society of Applied Physics.

Thermally enhanced photoinduced cooperative reorientation in hydrogen (H)-bonded polymer blend films was investigated. The films consisted of two kinds polymethacrylates with hexamethylene spacer groups terminated with 4-oxycinnamic acid (P6CA), 4-oxybenzoic acid (P6BA) or 4-(4'-oxyphenyl)benzoic acid (P6PBA) in the side chains. The films were subjected to linearly polarized ultraviolet (LPUV) light and subsequent annealing. Sufficient cooperative in-plane molecular reorientation in P6CA-P6BA blend films was achieved for the first time. In P6CA-P6PBA blend films, however, reorientation was not observed. The molecular weight, as well as the thermal properties of the homopolymers and the degree of photoreaction all played an important role in the cooperative reorientation behavior of the blend films. Finally, uniform alignment control of low-molecular-weight liquid crystals (LCs) on the molecularly reoriented polymer blend films perpendicular to the polarization E of LPUV light was obtained. (C) 2009 Elsevier Ltd. All rights reserved.

A detailed analysis of two-dimensional liquid crystalline grating cells is presented. Crossed liquid crystalline gratings were prepared using two kinds of photo-alignment polymers, i.e., poly(vinyl cinnamate) (PVCi) and photocrosslinkable polymer liquid crystal (PCLC). The effects of the anchoring strength of photo-alignment polymer films and crossing angles of grating vectors on one pair of photo-alignment substrates were extensively investigated using elastic continuum analysis, Jones calculus, and diffraction theory. The anchoring strength of our PCLC film was sufficiently strong, and experimental observation was in good agreement with the theoretical values obtained assuming the strong anchoring (fixed boundary conditions), although PCLC still has limits with the capability of photo-alignment of the low-molar-mass liquid crystals. ©2009 Optical Society of America.

Photoinduced reorientation of liquid crystalline polymethacrylates comprised of various lengths of alkylene spacers terminated with 4-oxycinnamic acid in the side chain and low-molecular liquid crystal (LC) alignment on the resultant photoreacted films were investigated using linearly polarized UV light. As the length of the spacer increased, the photoinduced optical anisotropy (Delta A) of the thin films increased, and Delta A increased as the irradiating temperature increased. Exposing the polymeric films in the LC temperature range of the material generated an in-plane molecular reorientation because the small photoinduced Delta A was simultaneously amplified. The low-molecular LCs aligned homogeneously on the photoreacted polymeric films, but the LC alignment direction depended on the alkylene spacer length and the degree of the photoreaction. (C) 2009 Elsevier Ltd. All rights reserved.

A detailed analysis of three-dimensional vector holograms is presented which were recorded in a photoreactive polymer dissolved liquid crystal. The diffraction properties of resultant periodic anisotropic structures were investigated. Experimental observations confirmed that the diffraction efficiencies of the structures varied with slight changes of the grating pitch, and also that they strongly depended on the incident angle of the probe beam. These diffraction properties were explained by the finite-difference time-domain optical simulations. © 2009 The Optical Society of Japan.

Diffractive optical devices using low-molar-mass liquid crystals are of great important for realizing numerical optical functions such as optical memory and information systems. In the present study the liquid crystalline gratings have been fabricated using a pair of photo-alignment substrates, and effects of the phase shift between the two photo-alignment substrates on the diffraction properties have been investigated. The liquid crystalline grating has been constructed with variable polarization dependence that can be controlled by the phase shift between the two photo-alignment substrates and twisted angles of the nematic directors. The theoretical considerations were also performed using the elastic continuum theory, Jones calculus, and diffraction theory. A guiding principle that controls the diffraction properties of the liquid crystalline grating cell was successfully presented. © 2009 Optical Society of America.

A fluorene monomer, which comprised 4-pyridylcyanovinyl groups (FL-CNPy), was synthesized, and the photolumineseenee (PL) properties of FL-CNPy combined with various (di)acids were evaluated. Due to hydrogen (H)-bonding or protonation between the pyridine end groups and acids, the PL emission maxima varied from 460 to 557 nm according to the acidity (pKa) and type of (di)acid. Additionally, adjusting the ratio of FL-CNPy/(di)acid tuned the PL emission wavelength without modifying the materials. Copyright © 2009 The Chemical Society of Japan.

Methacrylate polymer liquid crystals containing 4-(4-methoxycinnamoyloxy) biphenyl (MCB) side group with different alkylene spacer length between the polymethacrylate backbone and MCB side groups are synthesized. Influence of the alkylene spacer length on the thermally enhanced molecular reorientation behavior of thin films is investigated using linearly polarized ultraviolet (LPUV) light exposure and subsequent annealing. In-plane reorientation preferentially occurs when the alkylene spacer is short, and the induced in-plane order parameter is greater than 0.6. On the other hand, when the alkylene spacer is long, thermally induced out-of-plane reorientation is observed as well as the in-plane reorientation.

Poly(methacrylate) copolymer containing 95mol% of photoreactive H-bonded mesogenic unit 4-(6-hydroxyhexyloxy)cinnamic acid (6CA) and 5mol% of luminescent unit 2,7-bis[2-(4-hydroxyphenyl)-2-cyanovinyl]-9,9-dihexyl-9H-fluorene (CN-DHFP) was synthesized and characterized. The irradiation with LPUV light resulted in the induction of a small negative optical anisotropy (A) in the films due to the axis selective photoreaction of the cinnamic acid group. After annealing, the negative optical anisotropies both 6CA and CN-DHFP groups were significantly enhanced. The enhanced reorientation direction of both groups was perpendicular to E of LPUV light. Polarized blue emission was obtained with polarization ratio of about 2.0.

The cooperative molecular reorientation in methacrylate copolymer films with hexamethylene spacer groups terminated with photoreactive hydrogen (H) bonded 4-oxycinnamic acid (CA) and photoinactive 4-oxy-4'-methoxybiphenyl (MB) in their side chains was investigated by irradiating with linearly polarized ultraviolet light (LPUV) and subsequent annealing. A thermally enhanced cooperative in-plane orientation of both CA and MB side groups perpendicular to the polarization (E) of LPUV light was obtained when the annealing temperature was in the liquid crystalline temperature range of both mesogenic side group. On the other hand, thermal enhancement of the in-plane molecular reorientation did not occur when the annealing temperature was Out of the LC temperature range of the MB. It was clarified that the amount of axis-selectively photoreacted H-bonded CA groups and the LC mesomorphism of the copolymer film play an important role in the thermally enhanced cooperative molecular reorientation.

We have demonstrated the vector holograms using the radially polarized light. The inhomogeneous polarized light well controlled the spatial distribution of the optical anisotropy in the solid state polymeric materials. The theoretical calculation revealed formation mechanism and optical properties of the vector holograms. © 2009 American Institute of Physics.

Anisotropic diffractive gratings having periodic orthogonal molecular alignments are formed by a linearly polarized ultraviolet (LPUV) exposure through a photomask in hydrogen (H)-bonding liquid crystalline polymers (H-LCPs) using a unique molecular reorientation behavior. H-bonded side-chain groups of H-LCPs play an important role in the molecular reorientation and the resultant optical anisotropy originating from an intermolecular network composition. To evaluate its potential for optical applications, one- and two-dimensional diffractive gratings were fabricated and analyzed by both polarization optical microscopy and diffraction characteristics. As a result, anisotropic gratings using H-LCP were obtained with a high diffraction efficiency that was 80% of the theoretical maximum efficiency (33.9%) of thin diffractive gratings. Results of experimental and theoretical investigation reveal that the resultant molecular direction and optical anisotropy are generated and controlled by LPUV exposure. © 2009 American Institute of Physics.

We report the experimental results of two-dimensional patterning of colloidal crystals using edge-patterned cells. Solvent evaporation of a colloidal suspension from the edge of the cell induces self-organized crystallization of spherical colloidal particles. From a reservoir of colloidal suspension in the cell, different colloidal suspensions are injected repetitively. An edge-patterned substrate is introduced into the cell as an upper substrate. As a result, different colloidal crystals are alternately stacked in the lateral direction according to the edge pattern. The characteristics of cloning formation are specifically showed including deformations from the original pattern. This two-dimensional patterning of three-dimensional colloidal crystals by means of lateral autocloning is promising for the development of photonic crystal arrays for use in optic and photonic devices. © 2009 American Institute of Physics.

Polarization gratings with large birefringence are formed in photoreactive polymer liquid crystals with bistolane moiety and terminal cinnamic acid moiety by the use of polarized ultraviolet interference light and subsequent annealing. The polarized ultraviolet light causes the axis-selective photoreaction between the cinnamic acid groups and subsequent annealing induce the reorientation of peripheral molecules without cross-linking along the cross-linked groups. Long bistolane mesogenic moiety exhibits large birefringence in comparison with a biphenyl mesogenic moiety, the value of the induced birefringence in the bistolane mesogenic liquid crystalline (LC) polymer is strongly dependent on both the grating constant and the wavelength of the reconstruction light. © 2009 American Institute of Physics.

In the present paper, we extensively study the optical diffraction in two- and three-dimensional vector holograms and demonstrate the reconstruction of polarized optical images recorded in azobenzene-containing amorphous polymers (AP) and polymer-dissolved liquid-crystalline composites (PDLCC). The polarization states of the interference light are not modulated in the isotropic AP films, while modulated in the anisotropic PDLCC films. The information of the polarized optical image is recorded as the polarization induced anisotropy in the AP and PDLCC medium and is reconstructed as the polarized optical images. The theoretical consideration well explained the characteristics of the reconstructed polarized optical images from both two- and three-dimensional vector holograms. © 2009 American Institute of Physics.

Photo-cross-linkable liquid crystalline polymers (PLCPs) comprised of a 4-methoxycinnamoyloxy group connected with a tolane moiety possessing methyl substituents were synthesized in order to investigate the influence of methyl substituents on the thermally enhanced in-plane molecular reorientation of thin films. Different wavelengths from a UV light source were used to evaluate the effect of the photoreaction of the cinnamate and tolane moieties. For all PLCP films, thermally enhanced photoinduced molecular reorientation was observed, but the reorientation order and its direction greatly depended on the position and the number of the methyl substituents as well as the wavelength of light. A smaller degree of photoreaction was sufficient for effective molecular reorientation when the photoreaction of the tolane moiety was restricted. © 2008 American Chemical Society.

Light wave propagation in thick polarization gratings has been studied using the finite-difference time-domain (FDTD) method. The diffraction properties of the polarization Bragg gratings were strongly dependent on both the polarization state and incident angle of the probe beam. These characteristics were well explained by the FDTD calculation and the subsequent Fourier transformation. The FDTD calculation also revealed the light electric field near and/or in the polarization Bragg gratings. © 2008 The Japan Society of Applied Physics.

Thermally enhanced photoinduced in-plane molecular reorientation in new photo-cross-linkable polymer liquid crystalline (PPLC) films comprising 4-[ω-(4-methoxycinnamoyloxy)alkyloxy]biphenyl side groups is explored using linearly polarized ultraviolet (LPUV) light exposure and subsequent annealing. The influence of the alkylene spacer length between the photo-cross-linkable group and the biphenyl mesogenic moiety is investigated. The straight-line characteristics of the photoreactive mesogenic side group and the 4-methoxycinnamoyl group play important roles in the high photoreactivity and the large thermally enhanced molecular reorientation, where the in-plane order and the birefringence of the reoriented film are 0.61 and 0.18 are obtained. Finally, cooperative molecular reorientation of dichroic dyes doped in PPLC films is also achieved to fabricate a linear polarizer. © 2008 Wiley Periodicals, Inc.

Polymethacrylate copolymers, which have hexamethylene spacer groups terminated with 4-oxycinnamic acid, 4-oxybenzoic acid, and 4-(4'-oxyphenyl) benzoic acid in the side chain, were synthesized, and the photoinduced cooperative molecular reorientation of thin films was demonstrated using linearly polarized ultraviolet (LPUV) light and subsequent annealing. Adjusting the exposure doses can control the molecular reorientation direction both perpendicular and parallel to the polarization E of LPUV light. Tuning the copolymer composition adjusted the optical birefringence of homogeneously reoriented films between 0.095 and 0.178. Finally, adjusting the exposure doses achieved uniform alignment control of low-molecular liquid crystals (LCs) on the molecular reoriented copolymer films both perpendicular and parallel to the polarization E of LPUV light. © 2008 American Chemical Society.

Dicyclohexane-annelated anthracene was synthesized by a new efficient method, which employed the Diels-Alder reaction between in situ-generated 2,3-dehydronaphthalene and dicyclohexane-fused furan. The molecule adopted anti-parallel face-to-face slipped pi-stacking in its crystal structure. which induced an excimer-like emission in the solid state.

We have extensively studied the electric field of the light propagating in and/or near polarization holograms by the finite difference time-domain (FDTD) method. Polarization holograms were fabricated using photoreactive polymer liquid crystals and showed peculiar polarization conversion. This experimental observation is well-explained by the FDTD calculation. The FDTD calculation revealed the connection between the near and far field of the light transmitted through the polarization. ©2008 The Japan Society of Applied Physics.

In this paper, we describe the principle of the three-dimensional vector holograms formed in anisotropic recording medium. The polarization states of the interference light are three-dimensionally modulated due to both the polarization interference and optical anisotropy in the recording medium. The electric field of the polarized light reorients the director and forms the three-dimensional vector hologram in anisotropic photoreactive liquid-crystal composites. The theoretical consideration reveals the formation mechanism and optical characteristics of the resultant three-dimensional vector holograms. © 2008 Optical Society of America.

The formation of holographic polymer-dispersed liquid crystals was investigated in detail. The director was found to rotate during holographic recording owing to the change in morphology and migration of liquid crystals. A strongly anisotropic grating was constructed with variable diffraction efficiency that can be controlled by applying an analogue voltage to the nematic liquid crystal. Effects of post-curing on electro-optical properties were also investigated and the switching characteristics were strongly affected by the intermediate layer between the polymer and liquid crystal. © 2008 Taylor &amp Francis.

We present the results from some experimental and theoretical studies aimed at revealing the mechanism leading to the diffraction properties of two-dimensional cross polarization gratings in photocrosslinkable polymer liquid crystals. Although the polarization gratings are overwritten at the same place, each polarization grating works independently in our material system. The above-mentioned characteristic of our cross polarization gratings originates in the grating formation mechanism in the photocrosslinkable polymer liquid crystals, in which the molecules in the solid-state polymeric materials are not reoriented during exposure and reorientation is generated during the annealing process after multiple exposure. © 2007 Elsevier B.V. All rights reserved.

Highly functionalized birefringent films with a twisted nematic structure have been fabricated by axis-selective surface photoreaction and subsequent self-organization in photocrosslinkable polymer liquid crystals. The molecules at both film surfaces are selectively photoreacted owing to the strong absorption in the photoreactive material, and the resultant photocrosslinked mesogenic molecules induce the three-dimensional twisted structures in the film during the annealing process. Theoretical consideration was performed by assuming typical kinds of twisted structure, and we confirmed that the nematic directors are homogeneously twisted with fixed boundary conditions at the film surfaces. © 2008 The Japan Society of Applied Physics.

We investigated the diffraction properties of slanted anisotropic gratings originating from a photoinduced molecular reorientation of polymer-dissolved liquid crystal composites doped with trace amounts of an azo-dye. The diffraction efficiencies of the holographic gratings were strongly dependent on the incident angle and polarization state of the probe beam. In order to explain the properties, a model of the periodical reorientation distribution is presented, considering the relationship between the polarization state of the pump beam and the molecular reorientation of the material. The optical properties of the structures were simulated by employing the finite-difference time-domain (FDTD) method. The simulation results showed good agreement with the observed diffraction properties. © 2008 The Japan Society of Applied Physics.

We recently found that the chromonic mesophase structure of an azo dye can be immobilized by a silica network to form a chromonic-silica nanohybrid. This work reports the first demonstration of the macroscopic photoalignment and photopatterning of this nanohybrid via surface-mediated orientational transfer from a photocrosslinkable liquid crystalline polymer (PPLC). Irradiation with linearly polarized light (LPL) 300 nm above the PPLC film followed by an appropriate annealing process led to strong in-plane molecular orientation in the film. The precursor sol solution containing a chromonic forming azo dye and tetraethoxysilane in the presence of an anionic surfactant and 2-(2-aminoethoxy)ethanol was placed onto this aligned film by the static deposition or dipping method. After drying, the chromonic columns hybridized with silica were macroscopically oriented orthogonal to the LPL direction, namely the orientation of the dye molecule being parallel to it. In the dip coating process, a combination of photoalignment and flow induced orientation allowed clear micropatterning of the column orientations, which could be readily discerned when observed with a polarizing film. © The Royal Society of Chemistry 2008.

Light irradiation provides significant tools for material structuring and processing. In this article, the photo-orientation processes of the organic/inorganic hybrid materials recently achieved in our laboratory are briefly introduced. Irradiation of linearly polarized light to a polymer film containing a photoisomerizabke azobenzene or photocrosslinkable cinnamoyl unit leads to the induction of anisotropic molecular orientations on the surface. This molecular anisotropic surface structure can be transferred to a controlled orientation of nanostructures of organic/inorganic hybrid films at macroscopic scales. Two classes of lyotropic/silica systems have been applied to the photo-orientation procedures, i.e., ordinary surfactant systems and chromonic ones. These processes can be regarded as the extended applications of the so-called command surface systems, which photochemically regulate the molecular orientations of liquid crystals. © 2008 The Ceramic Society of Japan. All rights reserved.

Periodic anisotropic structures were induced by means of a three-dimensional vector holographic technique in an azo-dye-doped liquid crystal composite with uniaxial alignment. The three-dimensional vector hologram was fabricated by both the polarization interference and the polarization propagation in the anisotropic recording medium. In order to obtain clear insight into the optical properties of three-dimensional vector holograms, various types of structures were induced by changing the polarization states and incident angles of the recording beams. The diffraction properties of various types of three-dimensional vector holograms were calculated by the finite-difference time-domain method, and the theoretical explanations were in good agreement with the experimental results. © 2008 American Institute of Physics.

We have presented the results of some experimental studies aimed at quantifying the anisotropic holographic recordings in photoreactive polymer liquid crystals. In addition to the surface-relief gratings, index modulation gratings also appear during the holographic recording process, and the resulting dual gratings with strong anisotropy were characterized using the diffraction theory. The index modulation gratings showed strong optical anisotropy although the gratings were recorded by means of intensity holographic technique with only circularly polarized light. The experimental results including the induced birefringence were explained on the basis of the molecular migration. © 2006 Elsevier B.V. All rights reserved.

Thermally enhanced photoinduced reorientation in a photo-cross-linkable liquid crystalline polymethacrylate comprised of 4-(omega-cinnamoyloxyalkyloxy)biphenyl side groups is investigated by irradiating with linearly polarized ultraviolet (LPUV) light and subsequent annealing at elevated temperatures. An odd-even effect of the alkylene spacer length between the cinnamate end group and biphenyl group on the transition temperatures of the polymer, photoinduced optical anisotropy, and thermal amplification of the in-plane molecular reorientation of thin films are observed. Because of the higher straight-line characteristics of the mesogenic side groups with an odd number alkylene spacer, the axis-selectivity of the anisotropic photoreaction of the photoreactive groups is greater than that with an even number, which leads to a larger photoinduced optical anisotropy and effective molecular reorientation. Finally, the cooperative reorientation in composites of the polymer and nonliquid crystalline monomer is explored to amplify the reorientational order of the film. The resultant reoriented composite film exhibits an in-plane order parameter of 0.52 and birefringence at 633 nm of 0.15.

The cooperative molecular reorientation in methacrylate copolymer films with hexamethylene spacer groups terminated with 4-oxybenzoic acid (BA) and 4-(4-methoxycinnamoyloxy)biphenyl (MCB) in their side chains was investigated by irradiating with linearly polarized ultraviolet light (LPUV) and subsequent annealing. A high degree of cooperative in-plane reorientation of both the BA and MCB groups was obtained when the composition of the BA groups was greater than 50 mol% and hydrogen (H)-bonded LC mesogenic dimers of BA molecules existed. On the other hand, the molecular reorientation was restricted when the BA groups did not form H-bonds. It was clarified that the amount of axis-selectively photoreacted MCB groups and the H-bonds of the BA groups that exhibit a LC nature play important roles in the thermally enhanced molecular reorientation. © 2007 Elsevier Ltd. All rights reserved.

Twisted nematic gratings, originating from three-dimensional photoalignment of mesogenic molecules, have been recorded in azo-dye-doped liquid crystals by a polarization holographic technique. The three-dimensional distributions of the director were extensively investigated by considering the photoalignment of the azo-dye molecules and the resulting diffraction properties of the recorded gratings. The three-dimensional distributions of the director corresponded to the polarization modulation caused by light interference and to the propagation in liquid crystals with uniaxial optical anisotropy. These results suggest that the diffraction properties of the gratings can be controlled by the initial orientation of the liquid crystals and the polarization states of the recording beams. © 2007 The Japan Society of Applied Physics.

A detailed analysis of the recently proposed [Appl. Phys. Lett. 87 (2005) 161112] nematic phase gratings with photoregulated liquid crystal cells is presented. Nematic phase gratings with photoregulated photo-cross-linkable polymer liquid crystals were prepared and characterized. The phase grating consists of homogeneous and 90°-twisted nematic (TN) areas and shows unique polarization conversion in the diffraction process. The diffraction properties, including higher-ordered diffractions, were well explained by means of the elastic continuum theory, Jones calculus, and diffraction theory. © 2007 The Japan Society of Applied Physics.

In this letter, we describe the fabrication of a durable photoalignment layer for liquid crystals (LC) with high azimuthal anchoring and controllability of the tilt angle. A film is irradiated using linearly polarized ultraviolet (LPUV) light followed by annealing which induces the molecular orientation of the photoalignment layer. The nematic LC was aligned parallel to the electric vector of the LPUV light, and the alignment layer showed high thermal stability of the orientational characteristics up to 250°C. © 2007 The Japan Society of Applied Physics.

Methacrylate polymer liquid crystals containing p-substituted 4-cinnamoyloxybiphenyl (CB) side group were synthesized. Two vinyl end groups were introduced to investigate the influence of the end group on the photoinduced reorientation behavior. Thermally enhanced photoinduced orientation of polymer thin films was performed by irradiating with linearly polarized ultraviolet (LPUV) light and annealing. The reorientation behavior was evaluated by measuring the polarization absorption spectroscopy. When the degree of the photoreaction was around 10 mol%, the reorientation direction was parallel to the polarization of LPUV light for both polymer films. On the other hand, when the degree of the photoreaction was low, out-of-plane orientation was observed for the polymer with the longer end group.

The title compound, C28H16N2, also known as anthrazine, possesses a crystallographic center of inversion thus half of the formula unit is crystallographically independent. The hepta-cyclic ring system is essentially planar. In the crystal structure, the mol-ecular packing is characterized by a combination of a columnar stacking and a herringbone arrangement. Along the a axis, the mol-ecules in one column form face-to-face slipped π-stacks. The inter-planar face-to-face distance between neighboring mol-ecules is 3.495 (3) Å. © International Union of Crystallography 2007.

The industry of optoelectronics, including optical memeory, optical communication, and optical information processing, has developed since the last century. Over the past decade, interest has grown in nonlinear optical materials allowing operations in real time on the phase and on the amplitude of coherent wavefronts. Such nonlinear interaction is a fascinate subject, with great promise for application to image distortion compensation, coherent image amplification, optical image filtering, and novel laser resonator design. Photorefractive materials are by far the most efficient nonlinear optical media for optical wave mixing and phase conjugation, which are indispensable for the realization of most of photonics applications. Among many kinds of photorefractive materials, mesogenic materials show a high diffraction efficiency and relatively fast response under a low operating voltage. The aim of the present chapter is to summarize the development of the photorefractive mesogenic composites and to demonstrate optical information processing using photorefractive mesogenic composites. © 2007 Springer.

1,4,5,8-Tetra(alkyl)anthracenes (alkyl=methyl, ethyl, n-propyl, and n-hexyl) were prepared by a sequence of reactions of 1,2,4,5-tetrabromobenzene and 2,5-dialkylfurans in the presence of n-BuLi, hydrogenation, and treatment with acid. The influence of alkyl chain length on the packing patterns in the crystals and the fluorescent properties in the solid state was investigated. X-ray analysis revealed that the molecular structures can be classified into plane, semi-chair, and chair forms and that the packing patterns can be categorized into two-dimensional (herringbone) and one-dimensional (slipped-parallel) arrangements, in both of which there is no - stacking. In the case of the methyl, ethyl, and n-propyl derivatives, the wave shapes of the fluorescence spectra in the solid state resemble each other on the other hand, the n-hexyl derivative displayed a slightly red-shifted and broader spectrum. The absolute quantum yield depended on the transition dipole moments because of the packing patterns and crystal rigidity. The n-propyl derivative demonstrated the highest quantum yield of f=0.85 among the tetra(alkyl)anthracenes.

Two conformational polymorphs of 1,4,7,10-tetra(n-butyl)tetracene showed different characteristics of molecular structure, packing arrangement and optical properties in the solid state. © The Royal Society of Chemistry.

The title Cu complex with a tetradentate ligand, 1,2-bis(8-hydroxyqunoline-2-yl)ethane, was prepared and its crystal structure was determined by X-ray crystallography. The complex crystallizes in the triclinic system, space group P1 with with a = 8.1092(5), b = 9.2241(5), c = 10.8119(2)Å, α = 72.35(1), β = 79.13(2), γ = 81.53(2)°, V = 753.33(10)Å3, Z = 2. The copper atom is coordinated by two N atoms and two O atoms of two 8-quinolinolate moieties to form a significantly distorted tetrahedral geometry in the cis configuration. 2007 © The Japan Society for Analytical Chemistry.

The title compound, C16H10Br4, crystallizes in the monoclinic system, space group P21/c with cell parameters of a=14.525(5), b=6.588(2), c=16.327(6)Å, β = 93.440(4)°, V=1559.5(10)Å3, and Z = 4. The molecule adopts a butterfly- shaped roof structure with pseudo-C2v symmetry. 2007 © The Japan Society for Analytical Chemistry.

The polarization state of the diffraction light from the polarization holographic grating on varying the polarization conditions of the writing beams has been investigated on the basis of Jones theory. The authors found that the polarization holographic grating, which was fabricated by irradiating the two writing beams with around 0.2 of polarization ellipticity, could convert circularly polarized light into linearly polarized light, and the anisotropic phase grating under above-mentioned condition was really fabricated using the photo-cross-linkable polymer liquid crystal. This function, not observed in the conventional polarization gratings, should be widely applied as highly functionalized optical devices. © 2007 American Institute of Physics.

The liquid crystal phase gratings were prepared using a polarization holographic exposure on poly(vinyl cinnamate) or photocross-linkable polymer liquid crystal (PCLC) films. Anchoring strength between the photoalignment layer and low-molar-mass liquid crystal is a very important role to realize the liquid crystal grating as a practical optical device. Anchoring strength of our PCLC film is sufficiently strong and optical properties of liquid crystal gratings were theoretically well explained assuming the strong anchoring. © 2007 American Institute of Physics.

The photoinduced orientation in polymethacrylate, which has a hexamethylene spacer group terminated with a 4-oxycinnamic acid in its side chain (P6CAM), is explored using linearly polarized ultraviolet (LPUV) light irradiation. Because of the hydrogen- (H-) bonding among the cinnamic acid groups, P6CAM exhibits a liquid crystalline phase, and the axis-selective photoreaction of the cinnamic acid moiety generates the optical anisotropy of the film. When the exposed film is annealed or a virgin film is exposed to LPUV light at elevated temperatures, molecular reorientation both perpendicular and parallel to the polarization (E) of LPUV light is achieved, and the generated birefringence is 0.15. The orientation behavior of the film is determined by polarization UV and FTIR spectroscopies. Furthermore, the molecular orientation is erased by annealing at elevated temperature, while reexposing to LPUV light reorganizes the orientation. Finally, homogeneous alignment control of low-molecular liquid crystals on P6CAM films is demonstrated both perpendicular and parallel to E by adjusting the exposure energy.