The Effect of Molecular Structure of Side-Chain Azobenzene-Containing Polymers on their Photooptical Properties

Abstract
A comparative study of photoorientation processes occurring in amorphized films of three liquid crystalline comb-shaped azobenzene-containing polymers of acrylic and methacrylic series with different substituents in the chromophore group was carried out. Irradiation of these films with polarized blue light (473 nm) leads to the photochromic side group orientation in a direction perpendicular to the polarization plane of the incident light. A comparison of the photoinduced dichroism (D) for acrylic and methacrylic polymers revealed large D values for methacrylates and polymers with nonpolar substituents. Reorientation processes in the films were studied by irradiation of these films with the light of the same wavelength (473 nm) but the polarization plane was rotated by 90° with respect to the first irradiation cycle. A study of the reorientation process kinetics showed that all polymers are characterized by a decrease in the dichroism value compared with the direct process. This fact is explained by the homeotropic orientation of the side groups (azo chromophores) partially aligned along the axis of the light beam propagation.

Keywords: liquid crystalline polymers, photoinduced orientation processes, azobenzene-containing polymers, photooptics