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. Die 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 photoalignment of the LC, the LC hybrid cell using the PHSVAZO film achieved high LC alignment. The azo-attached polymer using the thermal reaction of vinyl ethers is useful for a photo-alignment material. Copyright (C) 2002 John Wiley Sons, Ltd.