Cooperative hydration, chain collapse, and flat LCST behavior in aqueous poly(N-isopropylacrylamide) solutions
Cooperative hydration, chain collapse, and flat LCST behavior in aqueous poly(N-isopropylacrylamide) solutions
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DOI：
10.1021/ma0502497
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发表时间：
2005-05-17
期刊：
影响因子：
5.5
通讯作者：
Tanaka, F
中科院分区：
文献类型：
--
作者：
Okada, Y;Tanaka, F
基于聚合物链与水分子（协同水化）之间的顺序氢键形成，从理论上推导了具有非常平坦LCST相分离线的聚n -异丙基丙烯酰胺（PNIPAM）水溶液的相图，并与实验spinodal曲线进行了比较。在PNIPAM溶液中，两相区域的形状随着协同性参数σ的变化而系统地发生变化，而在强协同水化（小σ）的情况下，spinodals几乎与聚合物的分子量无关。水合作用在很窄的温度范围内急剧发生。一条链上的氢键水分子的数目是作为温度和聚合物浓度的函数来计算的。
Phase diagrams with very flat LCST phase separation line for aqueous poly(N-isopropyl-acrylamide) (PNIPAM) solutions are theoretically derived on the basis of sequential hydrogen bond formation between polymer chains and water molecules (cooperative hydration) and compared with experimental spinodal curves. The two-phase region systematically changes its shape with the cooperativity parameter σ, and the spinodals turned out to be almost independent of the polymer molecular weight for strongly cooperative hydration (small σ) as observed in PNIPAM solutions. Hydration takes place sharply within a very narrow temperature region. The number of hydrogen-bonded water molecules on a chain is calculated as a function of the temperature and the polymer concentration.