Photo‐alignment material with azobenzene‐functionalized polymer linked in film

Application of a new azo-polymer as a photo-alignment material for liquid crystals (LCs) was demonstrated. 4-(Vinyloxyethyloxy)azobenzene (VAZO), which has thermally reactive vinyl ether groups, reacted with the OH groups of poly(4-hydroxystyrene) (PHS) during the baking process. The azo-attached polymer (PHS-VAZO) film showed anisotropic spectra after exposure to 365-nm linear polarized light (LPL) unlike the VAZO-doped poly(methylmethacrylate) (PMMA) film. The anisotropy of the film was small at high concentration of the azo-chromophore because of thermal randomization of the polarized state. In the evaluation of photo-alignment of the LC, the LC hybrid cell using the PHS-VAZO film achieved high LC alignment. The azo-attached polymer using the thermal reaction of vinyl ethers is useful for a photo-alignment material. Copyright © 2002 John Wiley & Sons, Ltd.