title: Photoreversible switching of the lower critical solution temperature in a photoresponsive host-guest system of pillar[6]arene with triethylene oxide substituents and an azobenzene derivative.
abstract: A new water-soluble thermoresponsive pillar[6]arene with triethylene oxide groups was synthesized. The pillar[6]arene showed lower critical solution temperature behavior in aqueous solution. Its clouding point was photoreversibly switched based on a photoresponsive host-guest system. The trans form of an azobenzene guest formed a stable 1:1 complex with the pillar[6]arene. Complexation increased the clouding point. Irradiation with UV light induced a conformation change for the azobenzene guest from the trans to cis form, and dethreading occurred because of a size mismatch between the cis form and the pillar[6]arene cavity. This dethreading decreased the clouding point. The photoresponsive host-guest system was reversible, and the clouding point could be switched by alternating irradiation with UV or visible light. We demonstrated photoresponsive reversible clear-to-turbid and turbid-to-clear transitions for the solution based on the reversible switching of the clouding point using the photosensitive host-guest system.
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan. ogoshi@t.kanazawa-u.ac.jp
authors.forename: Tomoki
authors.initials: T
authors.lastname: Ogoshi
authors.forename: Kanako
authors.initials: K
authors.lastname: Kida
authors.forename: Tada-aki
authors.initials: TA
authors.lastname: Yamagishi
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D005027:Ethylene Oxide / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D055668:Photochemical Processes; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012995:Solubility; D012996:Solutions; D013696:Temperature; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D001391:Azo Compounds; D000644:Quaternary Ammonium Compounds; D012996:Solutions; C581440:pillar(6)arene; C581441:triethylene oxide; D014867:Water; C009850:azobenzene; D005027:Ethylene Oxide