Photoisomerization-induced tunable LCST phase separation of azobenzene-containing polymers in an ionic liquid.
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.
Ueki
Takeshi
T
Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
Yamaguchi
Ayuko
A
Ito
Naoki
N
Kodama
Koichi
K
Sakamoto
Junji
J
Ueno
Kazuhide
K
Kokubo
Hisashi
H
Watanabe
Masayoshi
M
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
D001391:Azo Compounds; D052578:Ionic Liquids; D011108:Polymers; C009850:azobenzene