Molecular Crystals and Liquid Crystals, Vol.375, 769-783, 2002
3D orientational order in the photoaligning polymer films and its correlation with LC alignment
In this work we study correlation between spatial molecular distributions in the contacting anisotropic polymer films and LC layers. Two kinds of side-chain azopolymers were employed: with the azochromophores containing hydrophobic OC4H9 alkyl chain (P I) and strongly polar NO2 group (P2) as the end substituences, respectively. The tilt orientation of azochromophores was induced by the oblique irradiation of the polymer films with non-polarized UV light. The tilt angle was controlled by the change of the angle of the UV light incidence. The uniform alignment of several LC with the quasilinear dependence of the LC pretilt angle on the inclination angle of azochromophores was observed for the films of P I. In contrast, the alignment of LCs on the films of P2 strongly depended on the structure of LC molecules and did not depend on the inclination of azochromophores in the polymer bulk. Possible reasons of the difference in results obtained for P1 and P2 are discussed.