Concentration dependence of the Flory x parameter within two-state models
Concentration dependence of the Flory x parameter within two-state models
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DOI：
10.1021/ma020296o
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发表时间：
2002-07-30
期刊：
影响因子：
5.5
通讯作者：
Halperin, A
中科院分区：
文献类型：
--
作者：
Baulin, VA;Halperin, A
Flory chi参数通常被假定为仅取决于温度T。实验结果通常需要用chi（eff）代替chi（T），这也取决于单体体积分数，phi，chi（eff）（phi，T）。这种chi（eff）（phi，T）可以从两态模型中产生，提出了聚环氧乙烷（PEO）和其他中性水溶性聚合物。根据依数性可得到的预测的phi对bar的依赖性= chi（eff）-（1 - phi）偏导数chi（eff）/偏导数phi，在不同的模型之间有质的不同：（一）Karlstrom模型（物理化学杂志1985，89，4962）产生大于或等于0的对bar的偏导数（chi）/偏导数phi，而松山和Tanaka（Phys. Rev. Lett. 1990，65，341）和Bekiranov等人（Phys. Rev. E 1997，55，577）允许对bar/偏导数phi < 0的偏导数（chi）。(ii)利用用于拟合PEO相图的参数，从Karlstrom模型计算的（chi）对bar（phi）与实验值半定量地一致。另一方面，从Bekiranov等人的模型类似地计算出的（chi）/bar（phi）与测量结果有质的不同。总而言之，（chi）对bar（phi）为模型的性能提供了有用的度量。
The Flory chi parameter is typically assumed to depend only on the temperature, T. Experimental results often require the replacement of this chi(T) by chi(eff), which depends also on the monomer volume fraction, phi, chi(eff)(phi,T). Such chi(eff)(phi,T) can arise from two-state models, proposed for polyetheleneoxide (PEO) and other neutral water-soluble polymers. The predicted phi dependence of (chi) over bar = chi(eff) - (1 - phi)partial derivativechi(eff)/partial derivativephi, obtainable from colligative properties, differs qualitatively between the various models: (i) The model of Karlstrom (J. Phys. Chem. 1985, 89, 4962) yields partial derivative(chi) over bar/partial derivativephi greater than or equal to 0 while the model of Matsuyama and Tanaka (Phys. Rev. Lett. 1990, 65, 341) and of Bekiranov et al. (Phys. Rev. E 1997, 55, 577) allows for partial derivative(chi) over bar/partial derivativephi < 0. (ii) (chi) over bar(phi) as calculated from the Karlstrom model, utilizing the parameters used to fit the phase diagram of PEO, agrees semiquantitatively with the experimental values. On the other hand, (chi) over bar(phi) similarly calculated from the model of Bekiranov et al. differs qualitatively from the measured results. Altogether, (chi) over bar(phi) provides useful measure for the performance of a model.