Molecular Simulations of Solute Transport in Polymer Melts,ACS Macro Letters

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Molecular Simulations of Solute Transport in Polymer Melts
ACS Macro Letters ( IF 5.1 ) Pub Date : 2017-07-31 00:00:00 , DOI: 10.1021/acsmacrolett.7b00339
Kai Zhang ₁ , Sanat K. Kumar ₁

Affiliation

Polymer membranes are typically used to separate gas mixtures on the basis of molecular size differences (“sieving”). The gas purity is known to be inversely proportional to the membrane flux, and the slope of this plot in glassy polymers is empirically found to be determined by the sizes of the gas molecules being separated, λ = (d_B/d_A)² – 1. Despite potential mechanistic differences, the separation performance of rubbery polymers is often discussed in the same framework as their glassy counterparts. Here we perform molecular dynamics simulations of spherical solutes in coarse-grained high-density, high temperature polymer melts to gain a molecular understanding of their transport and separation behavior. We find that the diffusion coefficient follows an exponential law D ∼ e^–ad. Since this dependence results in λ = d_B/d_A – 1, these findings do not provide a direct understanding of the experimentally deduced slope of the Robeson plot.

中文翻译：

聚合物熔体中溶质运移的分子模拟

聚合物膜通常根据分子大小差异（“筛分”）用于分离气体混合物。已知气体纯度与膜通量成反比，根据经验，该曲线在玻璃状聚合物中的斜率取决于分离的气体分子的大小，λ=（d _B / d _A）²– 1.尽管存在潜在的机械差异，但橡胶状聚合物的分离性能通常在与玻璃状聚合物相同的框架内进行讨论。在这里，我们对粗粒高密度，高温聚合物熔体中的球形溶质进行分子动力学模拟，从而获得分子对它们的传输和分离行为的分子理解。我们发现，扩散系数呈指数规律d〜ë ^-广告。由于这种依赖性导致λ= d _B / d _A – 1，因此，这些发现无法直接了解Robeson图的实验推导斜率。

更新日期：2017-07-31

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