聚合物纳米复合材料 (polymer nanocomposite, PNC) 因其兼具纳米颗粒 (nanoparticle, NP) 和聚合物的性质而展现出较好的力学性能, 目前在材料领域和软物质科学研究中广受关注. 由于聚合物在多尺度动力学特征方面研究的困难性, 故预测聚合物在聚合物纳米复合材料中的扩散行为是一个亟待解决的问题. 采用耗散粒子动力学 (dissipative particle dynamics, DPD) 方法模拟了不同链长的聚合物在聚合物纳米复合材料中的扩散过程, 并用一个关键的无量纲约束系数 χ, 即聚合物链首末端距离 Lee 与有效自由扩散长度 Lf 的比值, 对聚合物链的扩散行为进行刻画. 通过分析纳米颗粒的浓度、聚合物链的长度和聚合物纳米颗粒之间的相互作用对聚合物扩散的影响, 提出了聚合物链的有效扩散率关于约束系数 χ 的标度率, 并证实该标度关系可以准确预测低约束系数 χ 时的模拟结果. 该工作对聚合物纳米复合材料的理论发展和应用研究有着一定的指导意义.

Polymer nanocomposites (PNCs) have shown excellent mechanical properties owing to their combinations of nanoparticle (NP) and polymer properties, and they are now of significant interest in the fields of materials and soft matter science. Considering the difficulties in determining their multiscale dynamic characteristics, predicting the diffusion behaviors of polymers in polymer nanocomposites remains an open problem. In this study, the diffusion processes of polymers with different chain lengths in PNCs are numerically simulated via the dissipative particle dynamics (DPD) method, and the diffusion behaviors of polymer chains are described by a key dimensionless constraint factor χ, which is the ratio of the distance Lee from the first end of the polymer chain to the effective free diffusion length Lf. By analyzing the effects of the concentration of NPs, the lengths of polymer chains, and the interactions between polymer NPs on polymer diffusion, a scaling rate for the effective diffusivity of polymer chains is proposed with respect to the confinement factor χ, and it is confirmed that this scaling law can accurately predict the numerical results with a low confinement factor χ. This study provides a guide for the theoretical development and application of PNCs.