Polymer diffusion is enhanced when nanorods (NRs) in a polymer nanocomposite are mobile relative to nanocomposites containing immobile NRs. NR mobility is tuned by varying the molecular weight of the matrix polymer and the NR concentration, and diffusion of deuterated polystyrene (dPS) tracers with varying molecular weight is studied using elastic recoil detection. When dPS diffuses faster than the NRs such that the NRs are “immobile” on the time scale of dPS, the tracer diffusion coefficient (D) monotonically decreases as the nanorod concentration increases; we interpret these results as though the nanorods provide additional topological constraints that slow diffusion of dPS. When the tracer diffusion is slow relative to NR diffusion (i.e., “mobile” NRs), diffusion is enhanced relative to the immobile NR case. This enhanced diffusion is captured by a slip-link model with two populations of topological constraints: one fixed population attributed to the PS matrix, and a second population of constraints with a finite constraint release time determined by the diffusion time of the NRs relative to dPS. These experimental and computational results provide fundamental insights into the nature of entanglements and constraint release in NR-containing polymer nanocomposites.

中文翻译：

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纳米棒流动性影响聚合物纳米复合材料中的聚合物扩散。

当聚合物纳米复合材料中的纳米棒（NRs）相对于含有固定NRs的纳米复合材料可移动时，聚合物扩散会增强。通过改变基体聚合物的分子量和NR的浓度来调节NR的迁移率，并使用弹性反冲检测研究了具有不同分子量的氘代聚苯乙烯（dPS）示踪剂的扩散。当dPS的扩散速度比NR快，从而使NR在dPS的时间尺度上“不动”时，示踪剂扩散系数（D）随着纳米棒浓度的增加而单调降低；我们将这些结果解释为纳米棒提供了额外的拓扑约束，从而延缓了dPS的扩散。当示踪剂扩散相对于NR扩散（即“移动” NR）缓慢时，扩散相对于固定NR情况会增强。这种增强的扩散是由具有两个拓扑约束种群的滑动链接模型捕获的：一个固定种群归因于PS矩阵，第二个约束种群具有有限的约束释放时间，该约束释放时间由NR相对于dPS的扩散时间决定。这些实验和计算结果为含NR的聚合物纳米复合材料中缠结和约束释放的性质提供了基本的见识。