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首页> 外文期刊>Journal of Applied Polymer Science >Thermodynamic study of a pressure-temperature phase diagram for poly(N-isopropylacrylamide) gels
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Thermodynamic study of a pressure-temperature phase diagram for poly(N-isopropylacrylamide) gels

机译：聚（N-异丙基丙烯酰胺）凝胶的压力-温度相图的热力学研究

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The volume change, &UDelta; V-h, accompanying the hydrophobic hydration associated with the volume phase transition in Poly(N-isopropylacrylamide) gels was measured by a simple method. The hydration accompanies a negative &UDelta; V-h-2.5 cm(3)/mol. The P-T phase diagram, the coexistence Curve, for the gels was determined from the swelling ratio-pressure curves up to 350 MPa for various constant temperatures. The contour of the coexistence curve is shaped like an ellipsoid on the P-T plain, which is a feature peculiar to the reversible pressure-temperature denaturation cf a protein. The thermodynamic analysis of the Clausius-Clipeyron relation for the measured &UDelta; V-h elucidates that the obtained coexistence curve represents the phase boundary between thermodynamic different phases like the two phases, native and denatured, of a protein and gives the transition enthalpy, &UDelta; H, 5.2kJ/mol by estimate, which well coincides with the transition heat measured by a calorimetric method. Considering the volume-dependent free energy, &UDelta;ν(mi) • P, for the mixing free energy of the gel, we can fit the calculated curve to the measured swelling ratio-pressure Curve of PNIPA gels. The value of &UDelta;ν(mi) changes the sign from negative to positive above around 100MPa. © 2005 Wiley Periodicals, Inc.
机译：音量变化＆UDelta;通过简单的方法测量V-h，伴随着与聚（N-异丙基丙烯酰胺）凝胶中的体积相变有关的疏水水合。水合伴随负的＆UDelta; V-h-2.5 cm（3）/摩尔。由各种恒定温度下直至350 MPa的溶胀率-压力曲线确定了凝胶的P-T相图，即共存曲线。共存曲线的轮廓在P-T平原上呈椭圆形，这是蛋白质可逆压力-温度变性所特有的特征。克劳修斯-克利佩龙关系的热力学分析，用于测得的＆Delta; V-h阐明了所获得的共存曲线代表了热力学不同相之间的相界，例如蛋白质的天然相和变性相这两个相，并给出了转变焓。 H估计为5.2kJ / mol，与通过量热法测得的转变热非常吻合。考虑体积依赖的自由能，＆ν（mi）＆BULL; P，对于凝胶的混合自由能，我们可以将计算的曲线拟合到PNIPA凝胶的溶胀率-压力曲线。 νν（mi）的值在100MPa以上将符号从负变为正。 ＆复制; 2005 Wiley期刊公司

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