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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.

Photochromic antiferroelectric liquid crystals containing a diazene moiety were synthesized for the first time, and their photochemical switching behaviors were studied.

Photochemical phase transition behavior of photochromic azobenzene liquid crystals (LCs) was explored by means of reflection-mode analysis. On pulse irradiation at 355 nm, which causes trans−cis is...

The unique features of the phosphonium salts as functional materials are reviewed, with emphasis being placed on the comparison between the phosphonium salts and the commonly available quaternary ammonium salts, which have the same structure, differing only in the positively-charged heteroatom. The antimicrobial activity of onium salts with different long-chain segments is described with special reference to structure–activity relationships. The unexpected relationship between the antibacterial activity and the aggregation behavior in aqueous solution (i.e. lyotropic liquid-crystalline properties) was revealed through systematic studies on the antibacterial activity of the phosphonium salts as a novel class of cationic biocides. Furthermore, it is shown that the phosphonium salts can act as thermotropic liquid crystals in spite of the fact that they are amphiphiles without a rigid core.

Vinylether was used as a cationically polymerizable moiety and incorporated into sidechain of polymers as copolymers of vinyloxyethyl methacrylate (VEM) and styrene (St). Photoirradiation of the copolymers containing a small amount of benzyl(4-hydroxyphenyl) methylsulfonium salt (BSS) resulted in a high crosslinking density as evidenced by a low degree of swelling, which is ascribed to the high reactivity of the vinyloxy moieties. The sensitivity of this photoreaction is significantly high because of a large kinetic chain length of the cationic polymerization of vinylethers, while copolymers of glycidyl methacrylate and St showed crosslinking to much less extent when irradiated under the same condition. The ability of other sulfonium salts, (4-hydroxyphenyl) methyl(4-nitrobenzyl) sulfonium salt and (4-hydroxyphenyl) methyl(1-naphthylmethyl)sulfonium salt, to induce photocrosslinking was also examined. © 1992 John Wiley & Sons, Inc.

The temperature dependence of excitation transfer between two identical chromophores (anthryl moieties) in α,ω-bis(9- anthryl)-n-alkanes [An(CH 2 ) m An (Am), with m=3, 5, 7, 10, 12, 14, and 18] in solid polymer matrix was investigated by time-resolved fluorescence anisotropy [r(t)] measurements. Using parameters determined from steady-state measurements and conformational analysis of Am, exatation hopping behariors at various temperatures were analyzed on the basis of Forster's mechanism

Nineteen 1,3-bis(aryl)propane derivatives and six model compounds with a single chromophore were used to explore the chiral discrimination ability of cellulose derivatives, in particular cellulose triphenylcarbamate (CTC), in connection with the mode of interaction of these probe molecules with adsorbents. The interaction was evaluated by conformational analysis of the probe moleculee and circular dichroism. The 1,3-bis(aryl)propanes with 9-anthryl moieties possessed a highly limited conformation owing to the bulky substituent and hardly changed their shape on CTC as evidenced by CD spectra

Liquid crystal (LC) polymers [CH 2 CH(COOR)] n (R= (CH 2 ) 3 OPhCOOPhOCH 3 , (CH 2 ) 3 PhPhCN) doped with azobenzene derivatived and LC copolymers [CH 2 CH(COOR)] x [CH 2 CH(COOR')] y (R= (CH 2 ) 3 OPhCOOPhOCH 3 ) were studied. Using a nanosecond pulsed laser, it was found that the relaxation time required for the nematic (N) to isotropic (I) phase transition was in a time range of 10 (copolymer)-100 ms (homopolymer doped with azobenzene) at T/T NN = 0.999, which was comparable to that of low molecular weight LC. Effects of temperature, laser power and structure of guest molecule were discussed

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-1-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.

The photochemically induced crosslinking of polymers having vinyloxy moieties in the side chain. Sulfonium salts used as photocatalysts initiated a cationic polymerization with high efficiency owing to a large kinetic chain length of the cationic polymerization of the vinylether moieties. The photoinduced crosslinking of polymers having epoxide side chains initiated by sulfoniumsalts was also reported.

Electroluminescent (EL) behavior has been evaluated in a cell which contained molecular dispersion of 1,4-bis(N,N-diphenylaminophenyl-1,3,4-oxadiazolyl)benzene (OXD) in a low-molecularweight liquid crystal, 4-octyloxy-4′-cyanobiphenyl (8OCB). EL emission was observed above the temperature where the OXD/8OCB mixture showed a liquid-crystalline phase. Furthermore, we fabricated an EL device which consisted of interdigital electrodes coated onto a glass substrate. It was found that the EL emission from the device was highly polarized.

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 Tg for several seconds, and rewritability was confirmed more than 100 cycles. No shrinkage was observed through those processes.

Hole drift mobilities of films of copolymers of acrylates with side‐chain mesogens and dimeric carbazoles were measured by the time‐of‐flight method. The copolymers were composed of acrylates with side‐chain phenylbenzoate or cyanobiphenyl and acrylates with side‐chain 1,2‐trans‐bis(9H‐carbazol‐9‐yl)cyclobutane (DCZB). Incorporation of the DCZB moiety into the copolymers resulted in homogeneous dispersion of the carrier molecules, but destabilization to a great extent of the liquid‐crystalline phase of the resulting copolymers. The hole drift mobility was found to be enhanced in copolymer films with more ordered structure of the DCZB moieties, indicating that orientation of the active molecules is favorable for the hole transport.

Hole drift mobilities have been measured in films of solid solution of trans‐1,2‐bis(9H‐carbazol‐9‐yl) cyclobutane (DCZB) in various host polymers; polymer liquid crystals (PLCs) and amorphous polymers. The hole drift mobilities were found to depend on the host polymers and be higher in PLCs. The larger mobilities of the DCZB/PLC mixtures have been attributed to the orientational effect of carrier molecules in the host PLCs.

Twin dimers containing 4-methoxycinnamic acid moieties at both ends of various lengths of ethylene glycol spacers (nEGMC) were found to exhibit liquid-crystalline phase behaviour, while those with cinnamic acid moieties (nEGC) at both ends did not show the liquid-crystalline phase behaviour. The liquid-crystalline phase behaviour of nEGMC depended on the length of the ethylene glycol spacers, n. Photoirradiation of nEGMC at >300nm resulted in the formation of photodimers through cyclobutane ring formation at the C=C part of the 4-methoxycinnamic acid moieties. The photoreaction was explored by following a decrease in vC=C (FTIR), formation of the photodimers (GPC) and structural analysis of the photoproducts (NMR). It was found that the morphology of the systems strongly affected the photoreactivity and the head-to-head photodimer was predominantly formed. The photoreactivity of nEGMC is discussed in relation to the morphology of the systems.

Emission properties of liquid-crystalline twin dimers containing 4-methoxy-cinnamic acid moieties at both ends of various ethylene glycol derivatives (nEGMC), where n denotes the number of the ethylene glycol units in the spacers, have been explored by steady-state and time resolved fluorescence spectroscopy in relation to the morphology of the system. Characteristic emissions were observed in the twin dimers, particularly in 2EGMC and 5EGMC, which were ascribed to excimer emission, and the energy gap between the locally excited state (monomer emission) and the excimer state and could be correlated to the difference in the spatial orientation of the mesogenic 4-methoxycinnamate groups adopted in nEGMC in the ground state. The picosecond time resolved fluorescence spectroscopy revealed no observed rise in the excimer emission in any sample at any temperature, indicating that the excimer is most probably formed by direct excitation of the pair wise arrangement of the 4-methoxycinnamate moieties in ...

Preparation des copolymeres photosensibles par semiesterification des copolymeres ethervinylique/anhydride maleique par le 6-(4-methoxyphenylazophenoxy) hexanol et par le 2-(4-methoxycinnamoyloxy) ethanol. Etude du comportement cristallin liquide, des transitions de phase photoinduites resultant de l'isomerisation cis-trans des groupes azo et mise en evidence de la reticulation photochimique par photodimerisation des groupes cinnamyl

Photochemical phase transition of polymer liquid crystals (PLCs) was explored for PLCs with mesogenic side-chain phenylbenzoate and cyanobiphenyl. The photochemical phase transition was triggered by photochemical reaction of photoresponsive molecules incorporated physically or covalently into PLCs as a result of lowering of phase transition temperature of the mixtures below the irradiation temperature. Factors affecting the photochemical phase transition are discussed and resolution of stored image was examined.

The optical switching behavior of azobenzene liquid crystals (LCs) was explored in terms of stability by means of reflection-mode analysis. The optical switching of the LC in the reflection-mode has been found to be repeated over 10 000 cycles, which is 10 times as stable as that obtained in the transmission-mode analysis although the same chromophore was used. It was found that the optimization of the optical system for material used is an effective approach to realize more stable optical switching.

Various kinds of crosslinked liquid-crystalline polymers were synthesized with acrylate monomers and diacrylate crosslinkers 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.

Etude du polyacrylate (CM 2 -CHCO 2 R 1 ) n -(CH 2 ) m -O-Ph-Ph-CW) dope par le 4-butyl 4'-methoxyazobenzene et du copolymere [(CH 2 -CHCO 2 R 1 -) x (CH 2 -CHCO 2 R 2 ) y ] n (R 2 =-(CH 2 ) m -O-Ph-N=N-Ph-OMe) L'irradiation des films de polymere entraine l'isomerisation reversible trans-cis qui induit la transition nematique → isotropique. L'efficacite de la transition depend de la valeur de m de la masse moleculaire du polymere et de l'ordre orientationnel initial du polymere

The orientational ordering of 4-n-pentyl-4′-cyanobiphenyl (5CB) was explored with the aid of picosecond, time-resolved fluorescence spectroscopy by monitoring the time dependence of excimer formation of the mesogen at various temperatures. It was found that in the nematic phase the excimer is formed with high efficiency, while in the isotropic phase the excimer formation was less effective. Immediately after pulse excitation the time-resolved fluorescence spectra revealed that short range ordering persists just above the N-I transition, although the macroscopic order had disappeared.

Comparison of PMMA end-labeled by 4-(N,N-dimethylamino) benzoate (DMAB) groups with monomer model compound (ethyl 4-(N,N-dimethylamino) benzoate; EtDMAB) and PMMA bearing a trace amount of DMAB on the side chain revealed that the twisting motion at the polymer end group was more facile than that of the polymer side chain and comparable to that of EtDMAB. When the degree of polymerization is increased, the end-group motion is suppressed slightly in a good solvent and strongly in a poor solvent

Etude de la transition de phase induite par la photoisomerisation dans les polyacrylates de ω-[methoxy-4' phenoxycarbonyl-4 phenoxy] alkyle dopes par un compose mesogene photoisomerable et dans les copolymeres du meme acrylate avec un acrylate de ω-(methoxy-4 phenylazo-4 phenoxy] alkyle. Relation avec la vitesse de la transition et la longueur de l'espaceur alcoxy et l'ordre orientationnel initial du polymere. Evaluation du polymere comme materiau de stockage d'image

Interaction of a polymeric in-chain quaternary ammonium salt with phospholipid bilayer membranes was studied by time-resolved fluorescence spectroscopy with the aid of a picosecond time-rcorrelated single photon counting system (instrument response function, 70 ps FWHM). Particular attention was paid to a phenomenon of polycation-induced fluidization of the membranes, which was well evaluated by time-resolved fluorescence anisotropy measurements. The fluorescence anisotropy, r ( t ), of 1,6-diphenyl-1,3,5-hexatriene (DPH) embedded in the membranes was analyzed based on the wobbling-in-cone model. Strong interaction was observed between the polycation and a negatively charged phosphatidic acid membrane as demonstrated by a large decrease of residual polarization value on adding the polycation to the acidic phospholipid dispersion. This means that the cone angle of the wobbling-in-cone motion of the DPH molecule increases by the addition of the polycaton, indicative of the polycation-induced fluidization of the acidic membrane. On the other hand, r ( t ) of DPH embedded in a zwitterionic phosphatidylcholine membrane was not affected significantly by the addition of the polycation, which is presumably due to non-binding of the polycation to the zwitterionic membrane. Our results clearly indicate that the polycationic disinfectant interacts strongly with negatively charged membranes, inducing fluidization of the membranes.

Determination par DSC des parametres thermodynamiques des transitions nematique-isotrope et des parametres d'ordre orientationnel de polyacrylates de ω-[methoxy-4' phenoxycarbonyl-4 phenoxy] alkyle et de copolymeres du meme acrylate avec un acrylate de ω-[methoxy-4 phenylazo-4 phenoxy] alkyle en fonction de la longueur de la chaine alkyl

New oligomers of in-chain quaternary ammonium salts as well as polymers were examined for antibacterial activity with special attention to the effect of their molecular weights. Two sets of homologs with different spacer structures were prepared: one with a rigid p-xylylene spacer and the other with a flexible hexamethylene spacer. It was found that the activity depends strongly on the molecular weight and that both bacteriostatic and bacteri cidal activity increase in the order of monomer — dimer < trimer < tetramer < polymer.

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 (~90%) and quick response (920 ms) was realized simultaneously.

The synthesis of donor-acceptor-type 2,5-diarylthiazoles that bear electron-donating N,N-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 N,N-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 N,N-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.

Muscle is a transducer that can convert chemical energy into mechanical motion. To construct artificial muscles, it is desirable to use soft materials with high mechanical flexibility and durability rather than hard materials such as metals. For effective muscle-like actuation, materials with stratified structures and high molecular orders are necessary. Liquid-crystalline elastomers (LCEs) are superior soft materials that possess both the order of liquid crystals and the elasticity of elastomers (as they contain polymer networks). With the aid of LCEs, it is possible to convert small amounts of external energy into macroscopic amounts of mechanical energy. In this Review, we focus on light as an energy source and describe the recent progress in the area of soft materials that can convert light energy into mechanical energy directly (photomechanical effect), especially the photomechanical effects of LCEs with a view to applications for light-driven LCE actuators.