橡胶纳米复合材料计算机模拟研究进展与挑战

总结了作者课题组采用分子动力学模拟研究橡胶纳米复合材料目前取得的主要进展,包括不同几何形状的纳米颗粒在橡胶基体中的分散机理、颗粒与橡胶分子链间的界面结合(聚合物玻璃化层是否存在)、颗粒对应力应变增强机理、碳纳米弹簧的引入对橡胶粘弹性的调控以及橡胶纳米复合材料非线性行为(Payne效应)产生的机理。模拟结果表明,存在一个最佳界面相互作用与接枝密度以实现纳米颗粒均匀分散;对于片状颗粒,在类似氢键界面相互作用时,存在聚合物玻璃化层。静态力学增强来自于两个方面:一是颗粒诱导分子链取向与排列,二是分子链吸附临近颗粒形成桥链在大变形下的有限链伸长。同时发现,碳纳米弹簧的加入会明显降低复合材料的滞后损失,并且得出纳米颗粒直接接触聚集与由分子链同时吸附多个颗粒成网对Payne效应非线性行为均有贡献。这些基础问题的澄清,将为制备动静态力学性能兼顾的橡胶纳米复合材料提供重要科学依据与理论指导,进而实现我国轮胎制品的高性能化与绿色化。最后针对橡胶纳米复合材料多层次多尺度结构与性能关系,简要评述了计算机模拟研究存在的挑战。

Achievements and Challenges of Computer Simulation Study of Rubber Nanocomposites

Here we summarize the current main progress in the aspect of rubber nanocomposites studied through molecu- lar dynamics simulation, including the dispersion mechanism of nanofillers with various geometrical shapes in rubbery chains, the interfacial interaction between fillers and rubbery chains （whether the glassy polymer layer exists ）, the strengthened mechanism of the stress-strain behavior, the adjusting of the visco-elasticity of rubbery chains by the intro- duced carbon nano-springs and the mechanism accounting for the non-linear behavior of rubber nanocomposites. The simu- lated results indicate that there exists an optimal interfacial interaction and grafting density to achieve a good dispersion of nanofillers. For the sheet-like nanoparticles（ NPs）, a glassy polymer layer is possible to exist in the case of the interfacial interaction similar to hydrogen bonding. The static mechanical reinforcement results from two aspects： one aspect is the a- lignment and orientation of polymer chains induced by NPs, and the other aspect is the limited extension of chain bridges formed by being adsorbed onto neighboring NPs at large deformation. The introduction of nano-springs will significantly re- duce the hysteresis, and direct contact between NPs as well as the network formed by each polymer chain simultaneously adsorbed onto several NPs both contribute to the formation of the non-linear behavior of the Payne effect. Elucidating these basic questions will provide significant scientific basis and theoretical guidance for preparing rubber nanocomposites with both excellent static and dynamic mechanical properties, further promoting the development of Chinese green automobile tires with high performance. Lastly, we briefly evaluate the challenges with regards to the structure-property relation of rub- ber nanocomposites investigated through computer simulation.