Effect of composition and stereoregularity on phase-transition behavior of aqueous N-ethylacrylamide/N-n-propylacrylamide copolymer solutions
Effect of composition and stereoregularity on phase-transition behavior of aqueous N-ethylacrylamide/N-n-propylacrylamide copolymer solutions
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DOI：
10.1016/j.polymer.2013.08.006
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发表时间：
2013-10
期刊：
影响因子：
4.6
通讯作者：
Tomohiro Hirano;A. Ono;Hiroaki Yamamoto;Takeshi Mori;Y. Maeda;M. Oshimura;K. Ute
中科院分区：
文献类型：
--
作者：
Tomohiro Hirano;A. Ono;Hiroaki Yamamoto;Takeshi Mori;Y. Maeda;M. Oshimura;K. Ute
N-乙基丙烯酰胺和N-正丙基丙烯酰胺（NNPAAm）以不同比例在-40 °C、在甲苯中、在3-甲基-3-戊醇存在下或在N-乙基乙酰胺中进行自由基共聚。合成了外消旋体含量为67.1- 70.2%的富间同立构共聚物和内消旋体含量为60.9-64.5%的富全同立构共聚物。NNPAAm组成≥ 92.9mol%的富间同立构共聚物在其水溶液的相变温度下表现出大的间同立构。NNPAAm组成为39.2- 67.6mol%的富含全同立构的共聚物在其水溶液的相变温度下表现出大的热稳定性。组成> 67.6mol%的那些不溶于水。立体序列分析表明，全同立构序列有利于相邻NNPAAm单元之间的分子内氢键，比间同立构序列。在全同立构序列中增强的分子内氢键是负责高NNPAAm组成的富含全同立构的共聚物的大的不溶性和不溶性。
Radical copolymerizations ofN-ethylacrylamide andN-n-propylacrylamide (NNPAAm) at various ratios were carried out at −40 °C, in toluene in the presence of 3-methyl-3-pentanol, or inN-ethylacetamide. Syndiotactic-rich copolymers withracemodiad contents of 67.1–70.2%, and isotactic-rich copolymers withmesodiad contents of 60.9–64.5% were prepared. Syndiotactic-rich copolymers with NNPAAm compositions of ≥92.9 mol% exhibited large hystereses in the phase-transition temperatures of their aqueous solutions. Isotactic-rich copolymers with NNPAAm compositions of 39.2–67.6 mol% exhibited large hystereses in the phase-transition temperatures of their aqueous solutions. Those of composition >67.6 mol% were insoluble in water. Stereosequence analysis suggested that isotactic sequences favored intramolecular hydrogen bonding between contiguous NNPAAm units, more than syndiotactic sequences. Enhanced intramolecular hydrogen bonding in isotactic sequences was responsible for the large hystereses and insolubility of isotactic-rich copolymers with high NNPAAm compositions.