Reversible photoresponsive chiral liquid crystal and multistimuli responsive organogels based on a cholesterol-azobenzene dimesogen

Abstract

An azobenzene-based mesogen with a CN group at one end and a cholesterol carbonate attached to the opposite end was synthesized. This compound is a reversible photoresponsive chiral liquid crystal, capable of the formation of multistimuli responsive organogels in organic solvents. The liquid crystalline, photo responsive and gelling properties as well as chiral induction and chiral amplification properties were demonstrated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscope (AFM), and affected by UV irradiation. The compound can act as a chiral mesogenic dye dopant to induce a highly helical twisting chiral phase in the common nematic phase of 5CB. This compound can show reversible photoresponsive properties in solution, in the liquid crystalline state and in the gel state. The gel formed by this compound in organic solvents can be reversibly modified under different environmental stimuli including light, temperature and shear. SEM and AFM reveal that the gelator molecules self-assemble into helical fibers of 58–130 nm in width and tens of micrometers in length and these fibers form three-dimensional networks.