2019 年 77 巻 3 号 p. 236-245
Self-assembled supramolecular architectures of amphiphilic diarylethenes featuring tri(ethylene glycol) monomethyl ether chains showed photoinduced macroscopic morphological change upon alternate irradiation with UV and visible light in water. These suspensions containing supramolecular assembly of the diarylethene showed absorption spectral shifts at temperatures corresponding to the lower critical solution temperature (LCST) transition. The photoreversible morphological transformation can be rationalized as the photoinduced phase transition between the high- and low-temperature phases of the LCST transition. Colorless microspheres of the open-ring isomer had bicontinuous coacervate structures. The closed-ring isomers became hydrated state and formed rod-like micelle and bilayer structures depending on intermolecular interaction. The photoinduced change in nanostructure enables application to sophisticated photoactuators in aqueous media. The nanofibers formed bundles in a methylcellulose aqueous solution by depletion force. A submillimeter-sized bundle showed a photoinduced shrinking of more than 100 µm under visible light irradiation. Elongation of the fiber was observed in the direction of linearly polarized light. The diffusive motion was suppressed in the direction perpendicular to that of the generated fiber, as revealed by means of trajectory tracking of added polystyrene beads. Photoinduced clustering of polystyrene beads and photocontrol of their diffusion was achieved with thermal convection and assistance of the change in supramolecular architectures.