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Dichroic dye layers were fabricated by spin coating of an aqueous dye solution on a thin film of an azobenzene polymer which was exposed to linearly polarized light in advance. The effect of polymer thickness on the dichroism and surface morphology of the dye layers were described.

In-plane alignment of nematic liquid crystals was regulated by polarized-light-irradiation of a cell assembled with a silica plate, the surface of which was modified by attaching 4-hexyl-4′-hexyloxyazobenzene at its o-position through surface silylation. The photoisomerizability of the chemisorbed azo-chromophore was affected by their surface density and the nature of photoinactive co-modifiers. The efficiency of the photoregulation of liquid crystal alignment was optimized by two-dimensional dilution of the chromophore with ethyltriethoxysilane (ETS) or 3-aminopropyltriethoxysilane (ATS). As a result, favourable procedure was to modify a silica surface with a crude azo-silylating reagent contaminated by ATS. The rate of the photoinduced reorientation of liquid crystals was followed by monitoring the alteration of the alignment direction of a dichroic dye dissolving in a mesophasic layer upon exposure to linearly polarized light. Exposure energy for the in-plane reorientation of a liquid crystal ...

Photoirradiation of a thin film of a homopolymer of 4-methacryloyloxyazobenzene with linearly polarized visible light, followed by cell fabrication, was found to generate a homogeneous alignment of nematic liquid crystals. In contrast, no alignment regulation was attained when the cell fabrication is made before photoirradiation, suggesting that the photo-induced persistent reorientation of the azo-chromophore is disturbed by penetration of the liquid crytal molecules into the polymer film to enhance the randomization of the oriented azobenzene chromophores

Quartz plates surface modified with a 6-nitrospirobenzopyran (SP) possessing a triethoxysilyl residue displayed photochromism. The polarity and interaction of SP with silanols at the surface are discussed on the basis of the absorption spectrum and thermal fading rate of the photomerocyanine form. When a nematic liquid crystal cell was fabricated with an SP-modified plate, azimuthal anisotropy of the nematic liquid crystal was caused by exposing the cell to linearly polarized UV light. The direction of the photo-induced homogeneous alignment was approximately perpendicular to the electric vector of the linearly polarized actinic light wave, and a photoimage was obtained by changing the polarization plane axis. The photo-induced in-plane alignment was scarcely altered even after prolonged storage at ambient temperature. Some attempts to regulate the alignment by irradiation with linearly polarized visible light for the reverse cyclization reaction failed.

Azimuthal anisotropy of a nematic liquid crystal alignment was caused by exposing 6-nitrospirobenzopyran monolayer to linearly polarized UV light. The photo-induced in-plane alignment was scarcely altered after prolonged storage at an ambient temperature.

Colloidal silver was prepared using various reductants such as hydrazine, ascorbic acid, ribose, and hydrogen in aqueous solution in the presence of copolymers of vinyl alcohol-N-vinyl pyrrolidone. The average particle size of colloidal silver decreased with increasing amount of copolymers added. The reduction by hydrogen provided smaller silver particles compared with the other reductants. The stability of colloidal silver against AlCl3 increased with increasing amount of copolymers added.

Precious metal particles (Au, Pt, Pd, Rh) were prepared using chitosan as a protective agent. The particle sizes decreased with increasing amounts of chitosan, while the dispersion stability against electrolyte increased. Similarly, stable bimetallic particles of AuPd and AuRh were obtained and their particle sizes were almost independent of feed composition. Furthermore, these bimetallic particles exhibited characteristic properties for the decomposition of hydrogen peroxide and hydrogenation of methylvinylketone.

A novel method to produce multiaxial polarizers has been developed. A thin film of poly(4-methacryloyloxyazobenzene) was coated on a substrate plate and irradiated with linearly polarized light to induce the reorientation of the azo chromophore. An aqueous solution of a dye was spread on the film by the spin-coating technique to form a dichroic dye layer. The direction of the electric vector of the polarized light for the photoisomerization determined the orientation direction of dye molecules.

Photochemical regulation of in‐plane alignment of a nematic liquid crystal is presented. A quartz plate surface was modified with 4‐hexyl‐4’‐hexyloxyazobenzene substituted with triethoxysilyl group through a spacer at the 2’ position to introduce the side‐on type azobenzene unit of the surface. A liquid crystal hybrid cell fabricated with the azo‐modified plate was irradiated with linearly polarized visible light for the n‐π* transition. This resulted in the in‐plane reorientation of the liquid crystal molecules to afford homogeneous alignment. Discussion is made on the mechanism of the in‐plane alignment regulation, and the concept of a molecular rotor is proposed.