Photo-Control of Chirality-Induced Liquid-Crystalline 3D Structures

Abstract

We investigated liquid-crystalline properties and photoresponse of a chiral azobenzene compound and found that it shows two kinds of highly-ordered liquid crystal phases. Studies on the optical textures and thermodynamic properties of the azobenzene compound suggest that the both mesophases are classified as the smectic Q (SmQ) phase which has been known as one of the chirality-induced three-dimensional (3D) liquid crystal phases. By the miscibility studies, one of the mesophases was confirmed to be T*I structure among the four structures of the SmQ phase. In a spectroscopic study of the chiral azobenzene compound in a tetrahydrofuran solution, it has been confirmed that a cis-trans photoisomerization can be induced by irradiation with ultra-violet light. Although the 3D structures are not sensitive to the applied electric field, we successfully demonstrate the “photo-switching” of these 3D structures by means of the photoisomerization.

Keywords:

• liquid crystal
• smectic
• chirality
• three dimensional structure
• photochemical phase transition
• smectic Q
• azobenzene