ALL-OPTICALLY CONTROLLABLE POLYMER LIQUID-CRYSTAL COMPOSITE FILMS CONTAINING THE AZOBENZENE LIQUID-CRYSTAL

Polymer/liquid crystal (LC) composite films possessing an azobenzene L C as a photoresponsive molecule (AzoCFs) were prepared by the thermal polymerization-induced phase separation method. The composite films (A zoCFs) showed a strong light-scattering state after polymerization, an d their optical properties were strongly affected by the compositional ratio of the liquid crystals in the composite film. Change in the tra nsmittance between a light-scattering and a transparent state could be induced isothermally by photoirradiation. Upon irradiation at 366 nm, AzoCFs changed from the light-scattering state to the transparent sta te. This is ascribed to nematic (N)-isotropic (I) phase transition due to trans-cis isomerization of the azobenzene molecules in the LC doma ins within the polymer matrix. Furthermore, restoration of the initial state could be achieved by visible-light irradiation (>420 nm), resul ting from the I-N phase transition induced by cis-trans back-isomeriza tion of the azobenzene guest molecules.