School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA.
J Chem Phys. 2010 Jan 14;132(2):024901. doi: 10.1063/1.3277671.
Coarse-grained, molecular dynamics (MD) simulations have been conducted to study the effect of shear flow on polymer nanocomposite systems. In particular, the interactions between different components have been tuned such that the nanoparticle-nanoparticle attraction is stronger than nanoparticle-polymer interaction, and therefore, the final equilibrium state for such systems is one with clustered nanoparticles. In the current study, we focus on how shear flow affects the kinetics of particle aggregation at the very initial stages in systems with polymers of different chain lengths. The particle volume fraction and size are kept fixed at 0.1 and 1.7 MD units, respectively. Through this work, shear has been shown to significantly slow down nanoparticle aggregation, an effect that was found to be a strong function of both polymer chain length and shear rate. To understand our findings, a systematic study on effect of shear on particle diffusion and an analysis of relative time scales of different mechanisms causing particle aggregation have been conducted. The aggregation rate obtained from the time scale analysis is in good agreement with that determined from the aggregation time derived from the pair correlation function monitored during simulations.
已进行粗粒化、分子动力学（MD）模拟，以研究剪切流对聚合物纳米复合材料系统的影响。特别是，已调整不同组件之间的相互作用，使得纳米颗粒-纳米颗粒吸引力强于纳米颗粒-聚合物相互作用，因此，此类系统的最终平衡状态是带有聚集纳米颗粒的状态。在当前研究中，我们关注剪切流如何影响具有不同链长聚合物的系统中颗粒聚集的初始动力学。颗粒体积分数和粒径分别固定在 0.1 和 1.7 MD 单位。通过这项工作，已表明剪切显著减缓了纳米颗粒的聚集，这种效应发现强烈依赖于聚合物链长和剪切速率。为了理解我们的发现，已对剪切对颗粒扩散的影响进行了系统研究，并分析了导致颗粒聚集的不同机制的相对时间尺度。从时间尺度分析得到的聚集速率与从模拟过程中监测的对关联函数得出的聚集时间确定的聚集速率吻合良好。
