Photoreversible Gelation of a Triblock Copolymer in an Ionic Liquid |
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| Authors: | Dr. Takeshi Ueki Yutaro Nakamura Ryoji Usui Yuzo Kitazawa Soonyong So Prof. Dr. Timothy P. Lodge Prof. Dr. Masayoshi Watanabe |
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| Affiliation: | 1. Department of Materials Engineering School of Engineering, The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku, Tokyo 113‐8656 (Japan);2. Department of Chemistry and Biotechnology, Yokohama National University, 79‐5 Tokiwadai, Hodogaya‐ku, Yokohama 240‐8501 (Japan) http://mwatalab.xsrv.jp/;3. Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. SE, Minneapolis, MN 55455 (USA);4. Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455 (USA) http://research.cems.umn.edu/lodge/ |
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| Abstract: | The reversible micellization and sol–gel transition of block copolymer solutions in an ionic liquid (IL) triggered by a photostimulus is described. The ABA triblock copolymer employed, denoted P(AzoMA‐r‐NIPAm)‐b‐PEO‐b‐P(AzoMA‐r‐NIPAm)), has a B block composed of an IL‐soluble poly(ethylene oxide) (PEO). The A block consists of a random copolymer including thermosensitive N‐isopropylacrylamide (NIPAm) units and a methacrylate with an azobenzene chromophore in the side chain (AzoMA). A phototriggered reversible unimer‐to‐micelle transition of a dilute ABA triblock copolymer (1 wt %) was observed in an IL, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C4mim]PF6), at an intermediate “bistable” temperature (50 °C). The system underwent a reversible sol–gel transition cycle at the bistable temperature (53 °C), with reversible association/fragmentation of the polymer network resulting from the phototriggered self‐assembly of the ABA triblock copolymer (20 wt %) in [C4mim]PF6. |
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| Keywords: | block copolymers gels ionic liquids self‐assembly sol– gel transitions |
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