Photochemical Control of the Macrostructure of Cholesteric Liquid Crystals by Means of Photoisomerization of Chiral Azobenzene Molecules

Chiral azobenzene compounds were prepared. A cholesteric phase was induced by mixing each azobenzene compound in a host nematic liquid crystal. A twisting power of the chiral azobenzene compounds was dependent on the distance between an azobenzene moiety and chiral moiety. The twisting power of the chiral azobenzene compounds was decreased by ultraviolet irradiation to cause trans to cis photoisomerization of the azobenzene compounds. The effects of the trans−cis photoisomerization on the phase structures of cholesteric liquid crystals, those that were prepared by mixing chiral azobenzene molecules and non-photochromic chiral molecules, will be discussed.