INFLUENCE OF A BRUSHED POLYIMIDE SURFACE ON PHOTOINDUCED REORIENTATION PROCESSES IN DYE-CONTAINING LIQUID-CRYSTALLINE POLYMERS

Infrared spectroscopy is used to study the influence of the polarizati on of the irradiating light and the substrate surface treated with pol yimide on the reorientation process of dye-containing liquid-crystalli ne side-group copolymers. The depolarization of the linearly polarized light on brushed polyimide surfaces affects the reorientation process and as a consequence the irradiation direction becomes the new order axis after irradiation. Relaxation processes are observed after short irradiation times, since a new stable equilibrium state has not been r eached. In contrast, complete reorientation, achieving changes in orde r parameter of 0.9, is observed after long irradiation times. The syst em is then stabilized in the new orientational distribution and no rel axation processes occur. The relaxation processes can be explained by a combination of matrix response and thermal cis-trans back relaxation of the azobenzene.