title: Photoisomerization-induced tunable LCST phase separation of azobenzene-containing polymers in an ionic liquid.
abstract: 4-phenylazophenyl methacrylate (AzoMA) and benzyl methacrylate (BnMA) were copolymerized to produce multistimuli-responsive polymers (P(AzoMA-r-BnMA)s) in a hydrophobic ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide ([C2mim][NTf2]), as the solvent. P(AzoMA-r-BnMA)s with a maximum of ca. 4 mol % AzoMA were soluble in [C2mim][NTf2] at low temperatures, and they underwent lower critical solution temperature (LCST) phase separation with an increase in temperature. Under UV and visible light irradiation, P(AzoMA-r-BnMA)s underwent reversible photochromism of trans-to-cis and cis-to-trans isomerization, respectively. The LCST temperature differences between trans- and cis-form polymers in the IL were as large as 22 degrees C. Reversible photoinduced phase separation of the polymers was achieved at a certain temperature; at this temperature, the cis-form polymers were soluble in the IL, but the trans-form polymers were not.
authors.affiliation: Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ueki
authors.forename: Ayuko
authors.initials: A
authors.lastname: Yamaguchi
authors.forename: Naoki
authors.initials: N
authors.lastname: Ito
authors.forename: Koichi
authors.initials: K
authors.lastname: Kodama
authors.forename: Junji
authors.initials: J
authors.lastname: Sakamoto
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Ueno
authors.forename: Hisashi
authors.initials: H
authors.lastname: Kokubo
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Watanabe
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D007536:Isomerism; D015394:Molecular Structure; D044367:Phase Transition; D010777:Photochemistry; D011108:Polymers / Q000737:chemistry*; D013696:Temperature
chemical_list: D001391:Azo Compounds; D052578:Ionic Liquids; D011108:Polymers; C009850:azobenzene