3A11 Relation between the pretilt angle of liquid crystal molecules and the photoinduced inclination angle of polyimide molecules containing azobenzene in the backbone structure

Abstract

We have investigated the pretilt angle of liquid crystal (LC) molecules induced by photoaligned films of polyimide containing azobenzene in the backbone structure. The polyimide films with different inclination of the backbone structure were prepared by performing photoalignment treatment for the corresponding polyamic acid films and then imidizing them thermally. The average inclination angle of polyimide backbone structure was determined by measuring the polarized infrared absorption spectra of the films as a function of the angle of incidence. The pretilt angle of LC molecules was determined by a crystal rotation method. A positive correlation (not linear relation) was found between the pretilt angle of LC molecules and the average inclination angle of the polyimide backbone structure.