Reversible thickness control of polymer thin films containing photoreactive coumarin derivative units |
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Authors: | Eriko Sato Sayoko NagaiAkikazu Matsumoto |
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Affiliation: | Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan |
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Abstract: | The reversible control of the thickness of polymer thin films was investigated using (meth)acrylic polymers containing photoreactive coumarin derivative units in the side chain. Coumarin derivative units underwent dimerization and the reverse-dimerization by photoirradiation and were used as a reversible cross-linking point. The homopolymer of 7-methacryloyloxy-4-methylcoumarin (Tg = 194 °C) did not cause changes in film thickness after photoreactions. The homopolymer of 7-(2′-acryloyloxyethoxy)-4-methylcoumarin (AEMC) (Tg = 89 °C) decreased 19% of film thickness by photodimerization and 73% of the decreased thickness was recovered after the reverse-dimerization and the subsequent thermal annealing at 130 °C. The reverse-dimerization of the copolymer of AEMC and n-butyl acrylate (AEMC content = 19 mol%, Tg = 11 °C) resulted in 53% of recovery from the decreased film thickness without annealing. The mobility of polymer main-chain was revealed to be essential factor to change film thickness by photoreactions. Photodimerization of coumarin derivative units in low glass transition temperature (Tg) tended to proceed faster than in high Tg polymers and resulted in larger decrease in film thickness. |
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Keywords: | Volume shrinkage Photo curing Photodimerization Glass transition temperature Reversible dimerization Coumarin |
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