Light induced spatial structures in the liquid crystalline azopolymers

We studied the 3D distribution of azobenzene fragments in the films of two comb-like liquid crystalline azopolymers before and after irradiation by ac tinic UV light using a null ellipsometry technique. The polymer with an alk yl chain C6H13 at the end of the azobenzene fragment forms structures with preferred homeotropic alignment of the fragments. Polarized UV light irradi ation at normal beam incidence induces biaxial structures with a preference for out-of-plane alignment of azobenzene fragments. High UV doses induce h ighly ordered homeotropic alignment of the fragments. The second polymer wi th polar NO2 group at the end of the azobenzene moiety shows preferential i n-plane orientation. Excitation with polarized light provides a highly orde red in-plane alignment of the azobenzene fragments perpendicular to the UV light polarization.