LIQUID-CRYSTAL FORMATION CONTROL OF POLYMER LIQUID-CRYSTAL MIXTURES BY PHOTOISOMERIZATION OF AZOBENZENE MOIETY

It is known that liquid crystalline molecules can exist with guest molecules in the liquid crystalline state. If the structure of guest molecule is greatly different from that of the host molecule, a small amount of guest molecule disturbs liquid crystalline structure and inhibits the formation of the liquid crystal in the system. Therefore, the formation of liquid crystal can be controlled by structural change of the guest molecules. In this study, the photoisomerization of azobenzene moiety was utilized for this structural change. Here, polymer having azobenzene moiety as a side chain was synthesized by esterification of OH groups of polymer. The liquid crystal formation was examined in the mixture of the polymer containing azobenzene moiety (photo-sensitive polymer) and a liquid crystalline compound of low molecular weight by DSC and polarizing optical microscope. Temperature range of liquid crystal formation of this mixture decreased linearly with the increase of the concentration of azobenzene moiety in the system as observed in the mixture of p-metho-xyazobenzene and a liquid crystal forming compound. It was confirmed that the liquid crystal formation is controlled by photoisomerization of azobenzene (trans to cis structural change). The masked image recorded by irradiation of 365 nm light is much stabler in the liquid crystalline mixture of photo-sensitive polymer than that in of p-methoxyazobenzene. © 1990, The Chemical Society of Japan. All rights reserved.