Photo-orientation in amorphous and aligned films of photochromic liquid crystalline polymers

Abstract

Optically isotropic films of liquid crystalline and amorphous copolymers containing azobenzene moieties were prepared and irradiated with linearly polarized light, thus generating an orientational order of the photochromic side groups. This process was compared with the photoinduced modification of the optical anisotropy in aligned liquid crystalline polymer films. It was demonstrated that the photo-orientation of the photochromic side groups resulted in a re-orientation of non-photochromic, rod-like side groups by a co-operative mechanism of this process even in the glassy state. Thus high optical anisotropy values were induced in initially isotropic films. The absolute values of the anisotropy and the kinetics of the induction process were investigated as a function of the structural features of the polymers.