Volumetric studies of aqueous polymer solutions using pressure perturbation calorimetry:: A new look at the temperature-induced phase transition of poly(N-isopropylacrylamide) in water and D2O
Volumetric studies of aqueous polymer solutions using pressure perturbation calorimetry:: A new look at the temperature-induced phase transition of poly(N-isopropylacrylamide) in water and D2O
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DOI：
10.1021/ma002082h
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发表时间：
2001-06-05
期刊：
影响因子：
5.5
通讯作者：
Winnik, FM
中科院分区：
文献类型：
--
作者：
Kujawa, P;Winnik, FM
我们报告的第一个应用程序的压力扰动量热法（PPC），以确定聚（N-异丙基丙烯酰胺）（PNIPAM）在H2O和D2 O的水化性能的解决方案进行温度诱导相变。该技术，它测量的热变化所产生的压力变化以上的PNIPAM的解决方案放置在微量热计单元，产生的热膨胀系数，α（p），在溶液中的聚合物和周围的聚合物链的溶剂化层的体积变化的温度依赖性。在低于和高于相变的温度范围内，PNIPAM在水中的α（p）随温度线性增加。在转变温度处，T-max急剧上升，然后迅速下降。相转变伴随着水合聚合物的部分比容的增加。与H2O相比，PNIPAM在D2 O中的溶液的这种增加显著更高。通过PPC对在水中经历胶束化的疏水改性的PNIPAM样品的相变的研究表明，聚合物胶束的水合作为疏水取代度和连接到聚合物的烷基的长度的函数显著变化。
We report the first application of pressure perturbation calorimetry (PPC) to determine the hydration properties of poly(N-isopropylacrylamide) (PNIPAM) in H2O and in D2O as the solutions undergo a temperature-induced phase transition. The technique, which measures the heat change resulting from a pressure change above a solution of PNIPAM placed in a microcalorimeter cell, yields the temperature dependence of the coefficient of thermal expansion, alpha (p), of the polymer in solution and the change in volume of the solvation layer around the polymer chain. In the temperature ranges below and above the phase transition, alpha (p) of PNIPAM in H2O increased linearly with temperature. It underwent a sharp increase at the transition temperature, T-max then rapidly decreased. The phase transition was accompanied by an increase in the partial specific volume of the hydrated polymer. This increase was significantly higher for solutions of PNIPAM in D2O, compared to H2O. A study by PPC of the phase transition of hydrophobically modified PNIPAM samples that undergo micellization in water demonstrated that the hydration of the polymeric micelles varies significantly as a function of the degree of hydrophobic substitution and length of the alkyl group linked to the polymer.