2C01 Photochemical control of the helical structure of cholesteric liquid crystals : Photoswitching between transparent and light scattering states

Abstract

Several chiral azobenzene compounds having different chiral substituents were prepared. Mixing a host nematic liquid crystal (E44) with each chiral azobenzene compound induced a cholesteric phase. The helical twisting power (HTP) as well as the change in the HTP by trans-cis photoisomerization is depended on the structure of chiral substituents. A compensated nematic phase was induced by combination of E44, a chiral azobenzene compound and a nonphotochromic chiral compound (Chiral). The compensated nematic phase was transformed into a cholesteric phase by UV irradiation, and the cholesteric phase was returned to the initial compensated nematic phase by Vis irradiation. The rate of switching between the compensated nematic and the cholesteric phase was closely related to the photochemical change in HTP.