Photochemical control of helical structure of cholesteric liquid crystals by means of photoisomerization of chiral azobenzene molecules.

Abstract

Three chiral azobenzene compounds were synthesized. A stable cholesteric phase was induced by mixing a host nematic liquid crystal and each chiral azobenzene. A twisting ability of a trans-form of the chiral azobenzene compound was found to be larger compared to that of cis-form. Next, a compensated nematic phase was prepared by mixing the chiral azobenzene, non-photochromic chiral compound in the host nematic liquid crystal. The mixture was transformed from compensated nernatic phase to cholesteric phase by the UV irradiation. Photochemically induced reversible switching of helical sense between left-handed and right-handed helices will be also discussed.