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首页> 外文期刊>The Journal of Chemical Physics >CORRELATION EFFECTS AND ENTROPY-DRIVEN PHASE SEPARATION IN ATHERMAL POLYMER BLENDS
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CORRELATION EFFECTS AND ENTROPY-DRIVEN PHASE SEPARATION IN ATHERMAL POLYMER BLENDS

机译：高分子聚合物共混物中的相关效应和熵驱动相分离

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Polymer reference interaction site model (PRISM) theory with the Percus-Yevick closure approximation has been applied to investigate the intermolecular correlations, effective chi-parameters, and spinodal phase separation of athermal binary polymer blends. These model mixtures an composed of structurally asymmetric semiflexible chains interacting via purely hard core potentials. In strong contrast to PRISM predictions for the idealized Gaussian thread model, nonlocal entropy-driven phase separation is predicted under certain conditions. By examining the intermolecular pair correlation functions we identify the physical driving force as local packing frustration associated with the different backbone stiffnesses of the blend components, which is propagated to macromolecular scales by chain connectivity and persistence. These entropic packing effects display many nonuniversal features including a sensitive dependence on chain length, blend composition, monomer volume difference, and both the mean and relative aspect ratios of the polymers. The sensitivity of the athermal blend fluctuation phenomena to local chain rigidity and nonzero liquid compressibility is emphasized. For model parameters characteristic of most flexible polymers of experimental interest the athermal packing frustration effect is found to generate only a small amount of thermodynamic incompatibility. Perturbative estimates of the enthalpic chi-parameters associated with (local) structural asymmetries suggest they are much more important than the purely entropic contribution for hydrocarbon alloys such as the polyolefins. Recent incompressible field theories for athermal conformationally asymmetric blends are derived within the liquid state integral equation framework by identifying an alternative, mean-field-like closure approximation coupled with the imposition of a zero compressibility constraint. (C) 1995 American Institute of Physics. [References: 70]
机译：聚合物参考相互作用位点模型（PRISM）理论与Percus-Yevick封闭近似法已被用于研究非热二元聚合物共混物的分子间相关性，有效chi参数和旋节线相分离。这些模型混合物由通过纯硬核电势相互作用的结构不对称的半柔性链组成。与理想高斯线模型的PRISM预测强烈相反，在某些条件下预测了非局部熵驱动的相分离。通过检查分子间对相关函数，我们将物理驱动力确定为与共混物组分的不同骨架刚度相关的局部堆积挫折感，其通过链连接性和持久性传播到大分子尺度。这些熵堆积效应显示出许多非普遍的特征，包括对链长，共混物组成，单体体积差异以及聚合物的平均和相对纵横比的敏感依赖性。强调了非热共混物波动现象对局部链刚度和非零液体可压缩性的敏感性。对于实验感兴趣的大多数柔性聚合物的模型参数特征，发现无热填料的挫折效应仅产生少量的热力学不相容性。与（局部）结构不对称有关的焓卡参的摄动估计表明，它们比碳氢化合物合金（如聚烯烃）的纯熵贡献重要得多。在液态状态积分方程框架内，通过确定与零压缩约束相关的，类似均值场的闭合近似，得出了非热构象不对称共混物的最新不可压缩场理论。 （C）1995年美国物理研究所。 [参考：70]

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