Metal-free isotactic-specific radical polymerization of N-isopropylacrylamide with pyridine N-oxide derivatives: The effect of methyl substituents of pyridine N-oxide on the isotactic specificity and the proposed mechanism for the isotactic-specific radical polymerization |
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Authors: | Tomohiro Hirano Hideaki Ishizu Tsuneyuki Sato |
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Affiliation: | Institute of Technology and Science, Tokushima University, Minamijosanjima 2-1, Tokushima 770-8506, Japan |
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Abstract: | The radical polymerizations of N-isopropylacrylamide (NIPAAm) in chloroform at low temperatures in the presence of pyridine N-oxide (PNO) derivatives were investigated. It was found that the methylation at meta-positions of PNO improved the isotactic specificity induced by PNO, whereas the methylation at ortho-positions prevented the induction of the isotactic specificity. NMR analysis revealed that NIPAAm and PNO derivatives formed predominantly 2:1 complex through a hydrogen-bonding interaction. Furthermore, the induction of the isotactic specificity was attributed to the conformationally limited propagating radicals. Based on these findings, the mechanism of the isotactic-specific radical polymerization was discussed. |
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Keywords: | N-Isopropylacrylamide Isotactic-specific radical polymerization Hydrogen bond |
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