Photochemical Control of the Helical Structure of Cholestreric Liquid Crystals -Effect of Structure of Chiral Azobenzene Molecules and Theoretica Study-

Abstract

Azobenzene compounds having chiral substituents were synthesized. Mixing each chiral azobenzene compound in a host nematic liquid crystal (E44) induced a cholesteric phase. We measured the helical twisting power (HTP) of the chiral azobenzene compounds before and after ultraviolet (UV) irradiation to cause trans-cis photoisomerization. Most of them were found to show the decrease in the HTP by UV irradiation. The magnitude of the HTP and the change in the HTP by UV irradiation were dependent on the structure of the chiral substituents, the number of the chiral substituents. The effect of the structure of the chiral azobenzenes will be discussed from the point of view of the experiments and chemical calculations.