Effects of end groups on phase transition and segmental mobility of poly(N‐isopropylacrylamide) chains in D2O
Effects of end groups on phase transition and segmental mobility of poly(N‐isopropylacrylamide) chains in D2O
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DOI：
10.1002/polb.22237
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发表时间：
2011-05
期刊：
影响因子：
--
通讯作者：
Geying Ru;Jiwen Feng
中科院分区：
文献类型：
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作者：
Geying Ru;Jiwen Feng
通过常规H-1核磁共振谱、自旋-自旋弛豫时间和二维NOESY谱的测量，研究了具有三种不同端基(羟基、碳-碳双键和樟脑磺酸基)的聚N-异丙基丙烯酰胺(PNIPA)链的相变和迁移率。结果表明，在室温下，PNIPA链的端基部分和端羟基部分的迁移率都高于双键和樟脑磺酸端基的PNIPA链。疏水双键端基和疏水双键端基修饰的PNIPA的低临界溶解温度分别与聚合物的相对分子质量成反比关系，而带有樟脑磺酸端基的PNIPA的临界溶解温度与聚合物的相对分子质量无关。双键端基与PNIPA链的内部链段同时坍塌，而羟基和樟脑磺酸端基在加热导致内链链段坍塌后仍表现出较高的迁移率，并且不会收缩紧密。推测羟基和樟脑磺酸端基位于球体表面，而双键端基可能埋入球体内部。(C)2011年威利期刊公司J Polym Sci第B部分：Polym Phys 49：749-755,2011
Phase transition and mobility of poly(N-isopropylacrylamide) (PNIPA) chains with three different types of end groups (hydroxyl, carbon-carbon double bond, and camphoric sulfonic groups) have been studied by measurements of the normal H-1 NMR spectrum, spin-spin relaxation time, and 2D NOESY spectrum. It is found that at room temperature not only the end group parts but also the part of the PNIPA chain with hydroxyl end group have higher mobility than corresponding parts of PNIPA with double bond and camphoric sulfonic end groups. The lower critical solution temperatures (LCST) of PNIPAs modified with hydrophilic hydroxyl and hydrophobic double bond end groups are inversely dependent and directly dependent on the molecular weight of polymer respectively, whereas the LCST of PNIPA with the camphoric sulfonic end group bearing both hydrophobic and hydrophilic structures is independent of the molecular weight. The double bond end groups collapse simultaneously with inner segments of the PNIPA chain, whereas the hydroxyl and camphoric sulfonic end groups still exhibit higher mobility and do not shrink tightly after heating-induced collapsing of inner segments. It is suggested that the hydroxyl and camphoric sulfonic end groups locate on the surface of globules, but the double bond end groups are probably buried inside the globules. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 749-755, 2011