Developments and Applications of Photoresponsive Molecular Assemblies

Abstract

Photo-induced morphological changes in the molecular assemblies formed by surfactants enable controlled release of incorporated substances, which can be applied in delivery systems of drugs, active components. In this article, we review the photoresponsive surfactants, which have been reported by our group. An azobenzene-based cationic surfactant represented changes in critical micelle concentration, accompanied by trans-cis photoisomerization with ultraviolet or visible light irradiation. A cinnamic acid-based photocleavable surfactant showed photoinduced changes in the interfacial properties, and also represented controlled solution viscosity and dispersibility of the nanoparticles. To realize on-demand control of the interfacial properties, the response speed by photoirradiation need to be fast. Recombination of lophyl radicals, produced from amphiphilic lophine dimers (3TEG-LPD) by ultraviolet light irradiation was enhanced in the confined space of the micelles. Surface tension of an aqueous solution of 3TEG-LPD decreased in several seconds upon ultraviolet light irradiation. in situ small-angle neutron scattering (SANS) system revealed 3TEG-LPD form elliptical micelles and the long axis was readily elongated by ultraviolet light irradiation. When the light irradiation was stopped, the morphology of the micelle readily recovered to the initial form. Solubilization capacity of the amphiphilic lophine dimer for a model drug was readily controlled by photoirradiation.