We present coarse-grained molecular dynamics simulations to probe chain-scale polymer conformations and diffusion between confining nanoparticles (NPs). By constructing a monolayer of hexagonally packed NPs in a polymer melt with athermal interactions, we observe the magnitude and length scale over which homogeneously confining NPs impact the polymer behavior, which provides fundamental insights into more complex polymer nanocomposites. We show that polymer conformations are more perturbed under strong confinement (i.e., when the interparticle distance, ID, is less than twice the polymer radius of gyration, 2R_g) as compared to around an isolated NP, and the effect depends on the ratio of R_NP/R_g rather than either independently. In fact, these conformations can be quantitatively replicated by executing a simple random walk in a similarly confining environment. We also show that polymer diffusion is slowed by the presence of NPs, and the slowing persists far beyond the length scale over which polymer conformations are perturbed. Although the slowing is strongest ∼R_g from the NPs, the diffusion coefficient is slower even beyond ∼5R_g from the NPs. Furthermore, by analyzing the directional van Hove distributions, we show polymer diffusion away from the NP monolayer is bulk-like while diffusion through the monolayer is slower with increasing NP confinement. These molecular dynamics simulations provide fundamental insights into the temporal and spatial effect of confining, athermal NPs on chain-scale polymer conformations, and diffusion.

中文翻译：

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聚合物构型和扩散通过约束纳米粒子的单层。

我们提出了粗粒度的分子动力学模拟，以探测链规模的聚合物构象和约束纳米粒子之间的扩散。通过在具有无热相互作用的聚合物熔体中构建六方堆积的NPs单层，我们观察了均匀围住NPs影响聚合物行为的幅度和长度尺度，这为更复杂的聚合物纳米复合材料提供了基本的见识。我们显示，与孤立的NP周围相比，聚合物构象在强约束下（即，当粒子间距离ID小于聚合物旋转半径2 R _g的两倍时）更易受到干扰，并且效果取决于比例的ř _NP / ř_克而不是独立。实际上，可以通过在类似限制的环境中执行简单的随机游走来定量复制这些构象。我们还表明，由于NP的存在，聚合物的扩散会减慢，并且这种减慢的持续时间远远超出了扰乱聚合物构象的长度尺度。虽然减慢最强〜ř_克从纳米颗粒，扩散系数是较慢甚至超出〜5 - [R_克从NPs。此外，通过分析范霍夫的定向分布，我们表明，随着NP约束的增加，聚合物从NP单层的扩散扩散为块状，而通过单层的扩散则较慢。这些分子动力学模拟提供了对约束，无热NPs对链规模聚合物构象和扩散的时间和空间影响的基本见解。