计算机模拟聚合物纳米复合材料导电导热的研究进展

We summarize recent progress in molecular dynamics simulation studies of the electrical and thermal conductivity of polymer nanocomposites. The simulation results show that a strong polymer-nanofiller interaction, a moderate chain functionalization degree, a moderate number of grafted chains, a moderate cross-linking density and an intermediate ratio of polymer blends all favor the formation of a conductive network, leading to enhanced conductive probability. In addition, an external shear field or electric field can induce orientation of the nanofiller along the external direction, which leads to a high anisotropy of the electrical conductivity. When the external fields are removed, the conductive probability gradually recovers its original value. This process can be described by a model. In the case of the thermal conductivity, the interfacial thermal conductivity is proportional to the grafting density, while it first increases and then saturates with increasing grafting length. Meanwhile, the intrinsic thermal conductivity of the nanofiller drops sharply as the grafting density increases. The maximum overall thermal conductivity of the nanocomposites appears at an intermediate grafting density because of these two competing effects. Meanwhile, the heat transfer process from one nanofiller to another can be approximately described by a thermal circuit model. Finally, a large increase in the thermal conductivity is observed when chains are grafted at the end atoms of nanofillers. Our work provides both a firm scientific basis and theoretical guidelines for preparing polymer nanocomposites with high electrical conductivity and high thermal conductivity.