1H HRMAS NMR Study on Phase Transition of Poly(N-isopropylacrylamide) Gels with and without Grafted Comb-Type Chains
1H HRMAS NMR Study on Phase Transition of Poly(N-isopropylacrylamide) Gels with and without Grafted Comb-Type Chains
复制标题
带或不带接枝梳型链的聚（N-异丙基丙烯酰胺）凝胶的 1H HRMAS NMR 研究
DOI：
10.1021/ma802780d
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发表时间：
2009-03-24
期刊：
影响因子：
5.5
通讯作者：
Feng, Jiwen
中科院分区：
文献类型：
--
作者：
Ru, Geying;Wang, Nian;Feng, Jiwen
本文用变温核磁共振氢谱和自旋-自旋弛豫时间研究了三种不同类型的聚（N-异丙基丙烯酰胺）凝胶（普通交联凝胶、梳型接枝凝胶和苯乙烯修饰梳型链的梳型接枝凝胶）的相转变。三种不同的凝胶表现出不同的崩溃行为，响应于增加的温度。对于普通凝胶，在32至35 ℃的相对窄的温度范围内发生显著的网络收缩。对于苯乙烯改性的梳型凝胶，总体链收缩出现在22 - 35 ℃的非常宽的温度范围内，其中苯乙烯改性的梳型链在比主链网络（32-35 ℃）更低的温度（22 - 32 ℃）下收缩。然而，在没有苯乙烯改性的梳型凝胶中，主链网络在加热时首先收缩（在32-35 ℃），然后梳状链塌陷（在35-36 ℃）。在骨架网络收缩过程中，梳形链被挤出主凝胶网络，这通过梳形链的异常T-2增加来揭示。T-2测量还表明，苯乙烯改性的梳型凝胶在平衡溶胀状态下具有更刚性的网络结构比传统的凝胶和梳型凝胶没有苯乙烯改性。
Phase transition occurring in three different types of poly (N-isopropylacrylamide) gels-normal cross-linked gel, comb-type grafted get, and comb-type grafted gel with styrene-modified comb chains-has been investigated by variable-temperature measurements of H-1 NMR spectra and spin-spin relaxation time. Three different gels exhibit distinct collapse behaviors in response to increasing temperature. For the normal gel, remarkable network shrinking occurs in a relatively narrow temperature range from 32 to 35 degrees C. For the styrene-modified comb-type gel, overall chain shrinkage appears in a very broad temperature range from 22 to 35 degrees C in which the styrene-modified comb chains shrink at lower temperatures (22-32 degrees C) than the backbone networks (32-35 degrees C). In the comb-type gel without styrene modification, however, the backbone networks shrink first (at 32-35 degrees C) on heating, followed by collapsing of comb chains (at 35-36 degrees C). During shrinkage of backbone networks the comb chains are expulsed from the main gel networks which is revealed by abnormal T-2 increase of comb chains. T-2 measurements also reveal that the styrene-modified comb-type gel in the equilibrium swelling state has more rigid network structure than both conventional gel and comb-type gel without styrene modification.