川月 喜弘

This paper describes the photoalignment behavior of composite thin films comprised of polymethacrylate with cinnamic acid side groups (pM6CA) and pyridine derivatives. Linearly polarized (LP) UV irradiation to composite films undergoes the photoreaction of cinnamic acid side groups, and the axis-selection is observed regardless of the content of pyridine derivatives. The negative dichroism is generated in all conditions and the photoinduced anisotropy is amplified when the exposed films are annealed. The photoinduced anisotropy and the exposure dose margin for the effective amplification of the molecular orientation improves when specific pyridine derivatives are doped with pM6CA. Using the reoriented pM6CA/pyridine derivatives composite films for the LC alignment layer, anti-parallel LC cell is prepared, where the LC alignment uniformity is related to the in-plane orientation order of the composite films.

Molecular alignment behavior of pentacene molecules sublimed on photoreactive liquid-crystalline polymer (PLCP) layer that are work as a photoalignment layer were explored. Pentacene molecule aligned perpendicular to the director of PLCP with edge-on to the substrate while pentacene on surface region of the bilayer forms the same structure as pentacene-alone substrate that covered the anisotropic edge-on pentacene structure on PLCP surface.

Facile fabrication of a photoalignable film from a nonphotoreactive polymethacrylate with 4-oxybenzaldehyde side groups (1) and a monomeric 4-methoxyaniline (2) composite is investigated. A 1/2 composite film fabrication and the annealing process form photoalignable N-benzylideneaniline (NBA) side groups, while the linearly polarized (LP) 365 nm light exposure to the resultant film induces sufficient molecular reorientation of NBA side groups. Furthermore, patterned coating of 2 on a 1 film and subsequent LP light exposure generate a patterned molecular orientation combined with controlled birefringence.

Holographic binary grating liquid crystal (LC) cells, in which the optical anisotropy was rectangularly modulated even as the grating was fabricated using holographic exposure, were fabricated by one-step polarization holographic exposure of an empty glass cell, the interior of which was coated with a photocrosslinkable polymer LC (PCLC). The present study is of great significance in that three types of holographic binary grating LC cells containing twisted alignments can be fabricated by simultaneous exposure of two PCLC substrates to the UV interference beams, which are sinusoidally modulated. The polarization conversion properties of the diffracted beams are explained well by theoretical analysis based on Jones calculus.

The thermally stimulated photoinduced in-plane and out-of-plane molecular reorientation behaviors of a polymethacrylate film comprised of 4-methoxycinnnamoylbiphenyl (MCB) side groups connected with a decylene spacer (PMCB10M) are compared in the bulk (>10 nm), at the inner-surface (similar to 10 nm), and at the near-surface (<2 nm) using polarized UV absorption and near-edge X-ray absorption fine structure (NEXAFS) spectroscopies. The biaxial reorientation characteristics in the bulk of the PMCB10 M films can be controlled by irradiating with linearly polarized (LP) UV light and subsequent annealing to generate self-organization of the MCB side groups. However, the homogeneous in-plane orientation at the near-surface, which can introduce homogeneous nematic low-molecular-weight liquid crystal mixture alignment, is observed regardless of the self-organization process. The differences in the orientation characteristics arise from long alkylene spacer and bulky mesogenic side groups.

The photoinduced reorientation behaviors of liquid crystalline (co)polymethacrylates (LCPs) comprised of N-benzylideneaniline (NBA) and 4-cyanobiphenyl or 4-methoxybiphenyl side groups are compared using linearly polarized (LP) 313 nm and LP 365 nm light. LCP films realize effective cooperative reorientation based on trans-cis-trans photoisomerization of the NBA moieties using LP 365 nm light and stabilization of the orientation structure due to copolymerization. In contrast, photochemical hydrolysis lowers the reorientation efficiency of LCP films when using 313 nm light. Changing the polarization direction of the LP 365 nm light controls the reorientation direction of the LCP films for several cycles, but the in-plane orientation order gradually decreases. Finally, LP 365 nm exposure and subsequent solvent annealing using a photo-cross-linked film achieve a repeatable write-erase-write of the orientation structure of the copolymer film.

Axis-selective photoreaction, photoinduced orientation of liquid-crystalline copolymers with N-benzylideneaniline (NBA) and phenylaldehyde derivative side group are explored. Irradiating with linearly polarized ultraviolet (LPUV) light generates coordinated molecular reorientation of the NBA side groups based on the axis-selective trans-cis-trans photoisomerization. of the NBA groups, but the reorientation performance depend on the copolymerization ratio. Furthermore, thermally stimulated amplification of the photoinduced optical anisotropy occurs upon exposing films to LP 365 nm light and subsequently annealing in the liquid crystalline temperature range of the materials.

Grating liquid crystal (LC) cell with twisted alignment was fabricated by using nematic LC doped chiral molecules (C15) and photocrosslinkable polymer LC as the alignment layer. The purpose of this study is to determine the doping effect of chiral molecules. As a result, disclinations are shifted by doping the chiral molecules. Furthermore, the dependence of plus and minus first-order diffraction properties on the chiral molecules concentrations are varied.

Two types of phenylenevinylene terthiophene with and without cyano side substitution were synthesized to investigate the effect of the molecular structure on optoelectronic properties. The oligothiophene with cyano side substitution exhibited large bathochromic effect and behaved as organic electron acceptors with decrease in field effect conductivity due to increase in dipole moment.

We present a universal polarization terahertz (THz) phase controller using a randomly aligned liquid crystal (LC) cell with graphene electrodes. The LC cell was fabricated using a nematic LC and two quartz substrates that were coated with a monolayer of graphene as the transparent electrode. The LC in the cell was prepared without any alignment treatments and was randomly aligned. The size of the random domains and the width of the disclination lines in the LC layer were several tens of microns. These textures disappeared when an alternating voltage was applied to the LC through the graphene layers. Using a THz time domain spectroscopic technique, we investigated the complex transmittance of the LC cell. The LC cell was highly transparent in the THz frequency range, and there was little change in the transmittance with the applied voltage. This indicated that the scattering loss originating in the randomly aligned LC molecules was small for the THz waves. We also demonstrated that the THz phase shift could be controlled by the applied voltage. The amplitude of the phase shift was explained by the ordinary and extraordinary refractive indices of the LC. These LC cells with graphene electrodes can be used to realize universal polarization THz phase controllers because of the random alignment.

Molecularly oriented surface relief (SR) formation in polymethacrylates with N-benzylideneaniline (NBA) derivative side groups is investigated by holographic exposure using a 325nm He-Cd laser. Because the NBA moieties show a photoinduced orientation perpendicular to the polarization of light, polarization holography successfully forms a molecularly oriented SR structure in accordance with the polarization distribution that includes p-polarized components. Although intensity holography induces molecular orientation, it does not generate a satisfactory SR structure. In all the holographic modes, the SR depth depends on the direction of the C= N bonds in the NBA moieties and the photoproducts affect the SR formation ability.

Blazed vector grating liquid crystal (LC) cells, in which the directors of low-molar-mass LCs are antisymmetrically distributed, were fabricated by one-step exposure of an empty glass cell inner-coated with a photocrosslinkable polymer LC (PCLC) to UV light. By adopting a LC cell structure, twisted nematic (TN) and homogeneous (HOMO) alignments were obtained in the blazed vector grating LC cells. Moreover, the diffraction efficiency of the blazed vector grating LC cells was greatly improved by increasing the thickness of the device in comparison with that of a blazed vector grating with a thin film structure obtained in our previous study. In addition, the diffraction efficiency and polarization states of ±1st-order diffracted beams from the resultant blazed vector grating LC cells were controlled by designing a blazed pattern in the alignment films, and these diffraction properties were well explained on the basis of Jones calculus and the elastic continuum theory of nematic LCs.

Mechanoresponsive luminophores containing different substituted pyridine rings at the molecular terminus are synthesized and their photoluminescence properties are investigated. The solid chromophore with a 4-substituted pyridine ring exhibits a reversible photoluminescent color change, while the 2-substituted chromophore shows only a small change in luminescence, and the 3-substituted chromophore displays an irreversible photoluminescent color change with mechanical grinding. A change of the sample color in response to mechanical grinding is also achieved for a dye-dispersed poly(vinyl alcohol) film. Furthermore, a simultaneous acid and mechanoresponsive photoemission color change is achieved in the dye-dispersed film.

Polarization-dependent near-edge X-ray absorption fine structure (NEXAFS) measurement is performed to investigate orientation structures of the near-surface of the reoriented photo-cross-linkable liquid crystalline polymer (PMCB6M) films, which are applicable to liquid crystal (LC) alignment layer. The 3D orientation parameter at the near-surface of the reoriented PMCB6M film is similar to 0.7, which is similar to the results obtained by a polarization absorption spectroscopy that evaluates the reorientation behavior in bulk. Furthermore, more preferable in-plane orientation is observed at the nearest surface of the film, and the phenyl rings in the reoriented mesogenic side groups show slightly perpendicular orientation to the surface normal.

Photoreactive liquid crystalline polymethacrylates with phenylbenzoate side groups with different molecular terminal were synthesized and their photoresponsive behavior was investigated. All polymer films underwent axis-selective photo-Fries rearrangement and generated photoinduced optical anisotropy upon exposure to linearly polarized ultraviolet (LPUV) light. In addition, annealing the photoreacted films enhanced molecular reorientation perpendicular to polarization direction of LPUV light, and the molecular terminal groups strongly affected the reorientation behavior.

The cooperative molecular reorientation in methacrylate copolymer films comprising photoreactive 4-(4-methoxycinnamoyloxy)biphenyl and phenylester in their side chains was investigated by irradiation with linearly polarized ultraviolet light and subsequent annealing. Both cinnamate and phenylester side groups were miscible in the copolymer composition, and axis-selective photoreaction of the cinnamate groups was observed. Thermally enhanced cooperative in-plane orientation of both side groups was obtained when the irradiated films were annealed in the liquid crystalline temperature range of the copolymers.

We have substantiated a simple yet efficient, competitive, and practical method to automatically fabricate liquid crystalline grating cells with homogeneous or twisted nematic (TN) structures by one-step ultraviolet holographic exposure on an empty glass cell coated with a photocrosslinkable polymer liquid crystal with 4-(4-methoxycinnamoyloxy)biphenyl side group (P6CB) films. The polarization diffraction properties in the resultant liquid crystalline grating cells have also been investigated extensively by varying the grating pitch. The theoretical considerations on the basis of elastic continuum theory revealed that accumulation of elastic free-energy density due to the TN structure affected the diffraction properties, although the strong anchoring of our photoalignment material contributed effectively to form the expected spatial distribution of liquid crystalline directors in the grating cells.

Multiblock copolymers consisting of poly(l-lactic acid) and poly(dimethyl siloxane) were prepared by the polycondensation of oligo(l-lactic acid) (OLLA) with dihydroxyl-terminated oligo(dimethyl siloxane) and dicarboxyl-terminated oligo(dimethyl siloxane). Copolymers with number-average molecular weights of 18,000-33,000 Da and various content ratios of oligo(dimethyl siloxane) (ODMS) unit were obtained by changing the feed ratio of these oligomers. A film prepared from the copolymer with an ODMS content ratio of 0.37 exhibited two independent peaks at -107 degrees C and 37 degrees C in the mechanical loss tangent for temperature dependence, suggesting the formation of microphase separation between the OLLA and ODMS segments. The film had a tensile strength of 3.2 MPa and a high elongation of 132%. The film also exhibited a high strain recovery even after repeated straining. The incorporation of dimethyl siloxane units as multiblock segments was confirmed to improve the flexibility of poly(l-lactic acid). (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40211.

A polarization holographic grating was recorded in a transparent thin film formed from polymethacrylate with N-benzylideneaniline (NBA) derivative side groups. We measured the real time diffraction properties. The data were analyzed based on a theoretical model that accounted for the distribution of optical anisotropy caused by molecular reorientation as well as for surface relief (SR) deformation caused by molecular motion. Optical anisotropy rapidly increased and then slowly decreased, with increasing recording time. This phenomenon was described based on photoisomerization and photocleavage reactions of the NBA side groups. SR deformation was also induced in the film by polarization holographic recording, without any subsequent processes. The photoinduced optical anisotropy and SR deformation were retained after the recording was turned off. © 2014 AIP Publishing LLC.

Multilevel anisotropic diffractive optical elements (DOEs), in which digitized spatial patterns of optical birefringence are fabricated by means of stepping photoalignment technique, has been demonstrated using photo-cross-linkable polymer liquid crystals (PCLCs). The polarization state of incident light is converted into a different polarization state by diffracting light in the practical, i.e., transparent in visible region and thermally stable, multilevel anisotropic DOEs, and both polarization azimuth and ellipticity can be widely controlled by their birefringence patterns. Theoretical considerations for such polarization conversion were also performed using the Jones calculus and diffraction theory and well-explained experimental observations.

Because of the potential for use in display applications, photoalignment using photosensitive materials has received considerable attention. Herein, the influence of film thickness on thermally stimulated photoinduced molecular reorientation structures of photoreactive liquid crystalline polymer films at the near-surface and in bulk is investigated using near-edge X-ray absorption fine structure (NEXAFS) and polarization UV absorption spectroscopies, respectively. In films less than 90-nm thick, the uniaxial in-plane orientation order in bulk gradually decreases. In contrast, films thicker than 40 nm show a sufficient molecular orientation at the near-surface. The three-dimensional orientation structures are investigated using obliquely reoriented films fabricated by slantwise p-polarized UV light exposure. Films thicker than 40 nm display an effective slantwise orientation in bulk, but the slantwise angle at the near-surface is much smaller than that in bulk. Both the substrate film interface and film thickness play important roles in the reorientation behavior not only in bulk but also at the near-surface of the photoalignment film.

This article presents effects of photocrosslinking on photorefractive properties in polymer-liquid crystal composites doped with fullerene (C 60) as a photoconductive agent. The efficiency of the photorefraction was improved by crosslinking the polymer network and reached near to the theoretical limit for the thin phase grating. The carrier conduction in the composite films was investigated and the high-performance photorefractivity of the photocrosslinked mesogenic composite was explained by low dark current and high photocurrent. The firm crosslinked polymer network in the polymer-liquid crystal composite has also employed for the stable photorefractive diffraction at elevated temperature and under a static dc field applied the mesogenic composite film. © 2013 Springer-Verlag Berlin Heidelberg.

A merged vector grating, which is holographically fabricated in an anisotropic medium by irradiation with interference light with intensity modulation and polarization modulation, was designed to detect the polarization of light. The merged vector grating is recorded by the interference of two elliptically polarized beams with equal intensities, parallel azimuths, equal ellipticities, and different directions of rotation. We clarified theoretically that the Stokes parameters of the incident light beam are described by the diffraction efficiency of the merged vector grating. Also, to apply this property to formation of a polarimeter without any moving parts or mechanisms, two merged vector gratings with different grating vectors were recorded in a photocrosslinkable polymer liquid crystal film by angle-multiplexed holography. By investigation of the diffraction properties of the gratings obtained, we demonstrated the applicability of the merged vector gratings for use in polarimetry. © 2014 AIP Publishing LLC.

Axis-selective photoreaction, photoinduced orientation, and formation of surface relief (SR) gratings of liquid crystalline polymethacrylates comprised of N-benzylideneaniline (NBA) derivative side groups are explored. Irradiating with linearly polarized (LP) 313 nm light generates molecular reorientation of the NBA side groups based on the axis-selective trans-cis-trans photoisomerization and photocleavage of the NBA groups. The in-plane order parameter (S) and birefringence (Δn) are ∼0.53 and ∼0.16, respectively. Furthermore, thermally stimulated amplification of the photoinduced optical anisotropy occurs upon exposing films to LP 313 nm light and subsequently annealing in the liquid crystalline temperature range of the material. The amplified S and Δn values are ∼0.71 and ∼0.21, respectively. Finally, polarization holography using 325 nm He-Cd laser beams with various interferometric polarization conditions demonstrates the formation of SR gratings with a molecularly oriented structure based on the periodic photoinduced reorientation and molecular motion. © 2013 American Chemical Society.

<p>Holographic recordings on liquid crystalline polymer film with N-benzylideneaniline groups (P1 and P2) are carried out using 325 nm laser with varying the polarization states. Great surface relief (SR) formation and molecularly oriented structure are investigated and analyzed their structure. As a result, for all polarization modes and concave area P1 and P2 revealed molecular reorientation when the exposing beams were linearly polarized. In P1 films, SR height was reach up to 230 nm. In contrast, P2 SR height was less than 100 nm.</p>

<p>A photo-cross-linkable liquid crystalline polymer (PMCB6M) film can be applicable to LC alignment layer. In case of LC alignment, a near surface structure of alignment layer is most important. We investigated three-dimensional molecular orientation of oblique aligned PMCB6M films in bulk and near surface determined by UV-vis absorption spectroscopy and near edge X-ray absorption spectroscopy (NEXAFS).</p>

<p>Supramolecular liquid crystal using the interaction of pyridine-carboxylic acid is known to many. On the other hand, previously, we have reported that the axis-selective anisotropy is generated by irradiating the LPUV light in the thin film of the hydrogen bonding liquid crystal polymers having a cinnamic acid in the side chain terminal, and the anisotropy is amplified in a perpendicular direction to the polarization electric field E by heat treating it in the LC temperature range. In this presentation, we report the results for the photo-alignment behavior when various pyridine compounds were added in this polymer.</p>

<p>Photoalignment can be applicable to optical information storage, polarization holography, and photoalignment of low-molecular-weight liquid crystals (LCs). To date, several types of photoreactive liquid crystalline polymers (PLCPs) realize an effective thermally stimulated photoinduced molecular orientation. We synthesized liquid crystalline polymer with N-benzylideneaniline (NBA) side group, and found that the polymer reoriented using LP light. In this study, in order to expand the cooperative molecular reorientation, I synthesize copolymer comprised of NBA sidegroup as photoreactive group, and cyanobiphenyl side group as non-photoreactive group.</p>

<p>Mechanochromic luminescence (MCL) is an isothermal change in photoluminescence in excess of two states, and at least one pathway is induced by mechanical stimuli such as grinding, s hearing, pressing and stretching. This property is expected for mechanical sensor, cellular imaging, detection of microenvironmental changes, and optical memory. In this work, we prepared novel liquid -crystalline MCL compounds containing acetylene or 1,2,3 -triazole in π-conjugated component. The dyes changed their photoluminescent color by mechanically grinding and reverted to initial state upon annealing at their liquid-crystalline temperture. In addition, the LC dye formed uniaxially alignment when it coa ted on photoalignment layer.</p>

<p>Charge transport properties of liquid crystalline semiconductors can be controlled by tuning their aggregation structure and orientational state. In the previous work, we synthesized liquid crystalline oligothiophene based on cyano vinyl terthiophene and investigated their molecular orientation behavior on the photo-alignment film. In this study, we reported electrical and optical properties of two types of liquid crystalline vinyl terthiophene with a nd without cyano side subst ituent and explored the effect of the cyano side group on the electrical properties.</p>

In this paper, we reported novel liquid-crystalline luminophore that switches its photoluminescent color by mechanically grinding. Mechanochromic luminescence (MCL) is expected for mechanical sensor, cellular imaging, detection of microenvironmental changes, and optical memory. In this work, we focused on liquid-crystalline MCL compounds on alignment layer. Controlling the molecular alignment of MCL compounds with photoalignment layer have potential to succeed in functional MCL film such as polarized micropatterned MCL and directional detection of mechanical stimuli. Herein, we prepared asymmetric rodlike MCL compounds containing cyano-and pyridyl molecular terminal and explored their photoluminescence behavior under mechanical stimulus. The cyano terminated compound showed a nematic phase and tuned its photoluminescent color from green to yellow upon grinding, while the pyridyl-terminated compounds that show no mesophase changed its photoluminescent color from blue to green and reverted to its initial color by heating above its melting point. The cyano-terminated MCL was aligned along the orientation direction of photoalignment layer and pyridyl-terminated MCL exhibited uniaxial alignment when it coated on photoaligned film containing carboxylic acid.

Vector gratings combined with form birefringence in subwavelength-periodic structures were experimentally fabricated by imprinting on polarization- sensitive liquid crystalline polymers and subsequent polarization holographic recordings. Polarization-sensitive optical diffractions were well controlled and the diffraction properties were dependent on the combination of periodic birefringence due to the reorientation of the mesogenic director and form birefringence originating in subwavelength-periodic structures. Finite-difference time-domain was an effective tool for characterizing the optical properties of the polarization holographic gratings with subwavelengthperiodic structures. © 2013 Optical Society of America.

Nonlinear light propagation in a dye-doped liquid crystal (LC) was investigated experimentally. A laser beam with wavelength far from the absorption peak of the material was coupled into an LC cell with homogeneous alignment, and the propagation in the cell was observed. When the polarization azimuth of the incident light was orthogonal to the orientation direction of the LC, soliton-like propagation was obtained for milliwatts of light power in spite of the low absorption. We clarified that the observed nonlinearity is due principally to the photothermal effect enhanced by the dye. © (2014) Trans Tech Publications.

Nonsinusoidal and asymmetric surface relief (SR) gratings, formed in azobenzene-containing polymeric films by elliptical polarization holographic recordings, were theoretically characterized. The amplitude of SR deformation was formulated on the basis of the optical-field gradient force model and calculated using the electric field of the interference light and the dielectric polarization of the recorded film. The observed SR gratings with asymmetric structures were well explained by considering the Weigert effect of azobenzene molecules. This observation suggests that SR deformation on the azopolymer film originating from mass transportation is affected by the distribution of optical anisotropy induced by the reorientation of the azobenzene molecules. © 2014 The Japan Society of Applied Physics.

The formation of polarization holographic gratings with both optical anisotropy and surface relief (SR) deformation was studied for polymethylmethacrylate with azobenzene side groups. Temporal contributions of isotropic and anisotropic phase gratings were simultaneously determined by observing transitional intensity and polarization states of the diffraction beams and characterizing by means of Jones calculus. To clarify the mechanism of SR deformation, cross sections of SR were characterized based on the optical gradient force model experimental observations were in good agreement with the theoretical expectation. We clarified that the anisotropic phase change originating in the reorientation of the azobenzene side groups was induced immediately at the beginning of the holographic recording, while the response time of the isotropic phase change originating in the molecular migration due to the optical gradient force was relatively slow. © 2013 Springer-Verlag Berlin Heidelberg.

The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus. © 2013 Springer-Verlag Berlin Heidelberg.

We recorded anisotropic gratings by polarization holographic recording in azobenzene-containing polymeric films doped with a 9-ethylcarbazole (ECZ) plasticizer. Using a polarimeter, we measured in real time the Stokes parameters of the beams diffracted from the gratings. We analyzed these data on the basis of a theoretical model that accounted for the distribution of birefringence caused by molecular reorientation as well as for surface relief deformation caused by mass transportation. Our results indicated that increasing ECZ doping level increased the formation speed of the anisotropic grating, but did not greatly affect the amplitude of the photoinduced birefringence. © 2014 The Japan Society of Applied Physics.

The cooperative molecular reorientation in methacrylate copolymer films comprising photoreactive 4-(4-methoxycinnamoyloxy)biphenyl and phenylamide in their side chains was investigated by irradiation with linearly polarized ultraviolet light and subsequent annealing. Both cinnamate and phenylamide side groups were miscible in the copolymer composition, and axis-selective photoreaction of the cinnamate groups was observed. Thermally enhanced cooperative in-plane orientation of both side groups was obtained when the irradiated films were annealed in the liquid-crystalline temperature range of the copolymers. (C) 2013 Elsevier Ltd. All rights reserved.

The molecular orientation of photoreactive liquid crystalline polymers can be controlled by linearly polarized ultraviolet (LPUV) irradiation and thermal treatment. Polymethacrylate with a hexamethylene spacer group terminated with 4-oxycinnamic acid on its side chain (P6CAM) is a photoreactive liquid crystalline polymer, and is reoriented parallel to the imprinted line upon thermal nanoimprinting. Thus, the molecular orientation of P6CAM could be controlled by LPUV irradiation or thermal nanoimprinting. Three dimensional molecular orientation may be induced in the P6CAM pattern by combining LPUV irradiation and thermal nanoimprinting (denoted hybrid nanoimprinting). Hybrid nanoimprinting of the photoreactive liquid crystalline polymer was carried out. © 2013 American Vacuum Society.

Asymmetric oligothiophenes with pyridine end groups, coated on a uniaxially aligned acid polymer film and subsequently annealed, exhibited large dichroism and linearly polarized photoluminescence parallel to the orientation direction of the aligned film. Furthermore, sublimation of the thiophenes during annealing was suppressed due to interaction with the acidic film.

Liquid crystal (LC) gratings with twisted alignment were fabricated by simple one-step polarizer-rotation exposure. An empty glass cell coated with photocrosslinkable polymer liquid crystal (PCLC) films was exposed by UV light with modulation of intensity or polarization. LC grating cells were obtained by filling the resultant cells with a nematic LC and the LC alignment structures were well controlled by both the intensity and polarization of the UV light. The diffraction properties of the LC gratings were explained by considering the periodic director distribution in the cells, estimated based on the elastic continuum theory of nematic LCs and the photoalignment effects of the PCLC films. © 2013 The Japan Society of Applied Physics.

Liquid crystalline poly(meth)acrylates (LCPs) with 4-methoxyphenyl thiobenzoate side groups were synthesized to attain a photoinduced molecularly oriented structure, which is transparent in the visible region. The axis-selective photoreaction and photoinduced reorientation behaviors of the thin films were investigated using linearly polarized (LP) 313 nm light. The axis-selective photoreaction of the side groups generated an optical anisotropy in all the LCP films, but the amplitude depended on the alkylene spacer length and the type of the polymer main chain. The photoirradiated films were transparent in the visible region because the photoreacted products expressed less color. The axis-selective photoreaction of films followed by the thermally generated self-organization processes effectively induced an in-plane molecular reorientation perpendicularly to light polarization with an in-plane order parameter (S) of 0.62 and birefringence (Δn) ∼ 0.17, when the mesogenic groups were connected to the polymer main chain via hexamethylene spacers. In contrast, the out-of-plane reorientation dominated when the LCPs contained long alkylene spacers. © 2013 American Chemical Society.