Alignments of nematic liquid crystal molecules on azo-dye-containing alternate self-assembled films investigated using attenuated total reflection method

Photoinduced in-plane alignments of nematic liquid crystal (LC) molecules, 5CB, have been investigated in a LC cell prepared with alternate self-assembled films of polyelectrolytes and low-molecular-weight azobenzene molecules on gold electrodes using the attenuated total reflection (ATR) measurement method. A high dichroism of the self-assembled film was observed with the irradiation of linearly polarized light. The ATR properties due to excitations of surface plasmon polaritons (SPP) were observed in the LC cell and changed with the irradiation of linearly polarized visible light to the LC cell. The experimental results corresponded well with the calculated shifts at different orientation states of 5CB molecules. It was estimated that the LC molecules have in-plane alignments and that the LC molecules are oriented perpendicular to the polarization direction of the irradiated visible light. The molecular orientations could be controlled by the polarization direction of irradiated light on the hybrid LC cell. In-situ observations for the cell were also carried out during the irradiation. Furthermore, the thickness and dielectric constants of the self-assembled films were evaluated using the ATR method.