Formation of Photoresponsive Physical Organogels by a Liquid-Crystalline Gelling Agent with an Azobenzene Moiety

Abstract

We found gelling ability of liquid-crystalline azobenzene compound I containing a chiral carbonate moiety with a higher order smectic phase. The compound functioned as a gelling agent for various organic solvents such as diethyl ether, dodecane, and 2-propanol. The AFM images of the xerogels derived from these organogels showed that fibrous aggregates form network structures. The isothermal transition from gel to sol was induced for a 2-propanol/1 gel by the photoirradiation of the gel at 366 nm, which caused trans-cis isomerization of the azobenzene moiety of 1. The sol-gel transition was also induced by the irradiation at 436 nm to the resulting sol. The sol-gel phase transitions could be reversibly controlled by the trans-cis photoisomerization of 1.