Photoinduced surface alignment: The role of liquid-crystalline order

The optical control of surface alignment was investigated, using ate-dye do ped polyimide films as photosensitive material. The kinetics of the realign ment of the easy axis was measured in isotropic, nematic and smectic A phas es, It is demonstrated that the light-induced realignment of the dye molecu les at the polymer-liquid crystal interface is strongly influenced by the p resence of the liquid-crystalline order. A simple model is presented, which accounts qualitatively for the experimental observations.