Two Findings Obtained from the Synthesis and Synthetic Process of a Photo-responsive Surfactant – Photo-induced Demulsification and Gold-colored Crystals

Abstract

A novel surfactant (C7-azo-C7) containing an azobenzene skeleton has been synthesized and stable oil in water (O/W)-type emulsions consisting of n-octane and water have been prepared. Ultraviolet (UV) light irradiation of the emulsions promotes the cis isomerization of trans C7-azo-C7 and leads to the coalescence of the oil (octane) droplets in the emulsions, that is, demulsification. In the course of the C7-azo-C7 synthesis, a synthetic intermediate has been found to form gold-colored crystals. It is found that the molecules produce J-aggregates in the crystals. Water molecules in the crystals will be essential for the formation of the stable J-aggregates and the resultant gold luster.