A photoresponsive planar chiral azobenzene dopant with high helical twisting power

Abstract

A planar chiral molecule as a photon-mode chiral switch was synthesized for the reversible control of self-assembled superstructures based on doped chiral nematic liquid crystals. The chiral switch is composed of bis-hexyl substituted diphenylnaphthalene and a photoisomerizing azobenzene unit connected by ethylene spacers in a cyclic manner. Bis-hexyl substitution to the mesogenic unit promoted the chirality transfer to the host LC medium resulting in a high initial helical twisting power (HTP) and a large change in HTP by photo-isomerization of the chiral dopant. At very low doping concentrations, both reversible tuning of RGB reflection colors and rotation motion control of micro glass rods on the cholesteric liquid crystal surface were achieved.