Effects of Hofmeister anions on the LCST of PNIPAM as a function of molecular weight
Effects of Hofmeister anions on the LCST of PNIPAM as a function of molecular weight
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DOI：
10.1021/jp0690603
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发表时间：
2007-06-28
影响因子：
3.7
通讯作者：
Cremer, Paul S.
中科院分区：
文献类型：
--
作者：
Zhang, Yanjie;Furyk, Steven;Cremer, Paul S.
采用温度梯度微流控装置，在暗场显微镜下研究了不同钠盐对聚n -异丙基丙烯酰胺（PNIPAM）低临界溶液温度（LCST）的影响及其与分子量和浓度的关系。在含有足够浓度的宇宙向阴离子的溶液中，对于高分子量样品，PNIPAM的相变被分解为两个独立的步骤。这两步过渡的第一步被发现对聚合物的分子量和溶液浓度敏感，而第二步则不敏感。此外，各向异性阴离子与聚合物的结合也受分子量的影响。这两组结果都可以用聚合物链之间分子内和分子间氢键的形成来解释。相比之下，发现异丙基部分和聚合物主链的疏水水合作用不受聚合物分子量或溶液浓度的影响。
The effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated as a function of molecular weight and polymer concentration with a temperature gradient microfluidic device under a dark-field microscope. In solutions containing sufficient concentrations of kosmotropic anions, the phase transition of PNIPAM was resolved into two separate steps for higher molecular weight samples. The first step of this two-step transition was found to be sensitive to the polymer's molecular weight and solution concentration, while the second step was not. Moreover, the binding of chaotropic anions to the polymer was also influenced by molecular weight. Both sets of results could be explained by the formation of intramolecular and intermolecular hydrogen-bonding between polymer chains. By contrast, the hydrophobic hydration of the isopropyl moieties and polymer backbone was found to be unaffected by either the polymer's molecular weight or solution concentration.