纳米粒子增强聚合物复合材料分散机理的计算机模拟研究

Nano-particle reinforced polymer-based composites have attracted extensive interests in polymer material science, which are of great scientific importance and industrial perspective. The key to produce the polymer-based nano-composites with high mechanical performance is to obtain a uniform dispersion of the nano-particles in polymer matrix which requires a comprehensive understanding of interfacial phase behavior of the particle-polymer system on molecular length scale. The investigation of the effects of particle surface and polymer characteristics on interfacial binding and dispersion allows us to fully understand the nature of dispersion. This project application will focus on the study of the miscibility of the interface between nano-particle and polymer phases by performing Monte Carlo and molecular dynamics simulations with statistical thermodynamic theory. By developing high efficient theoretical models, the effects of surface properties, molecular weight polydispersity, as well as chain stiffness on dispersion state will be studied. The quantitative dependence of the inferfacial micro-structures and dynamics on particle curvature, molecular weight, strength of interfacial interactions and grafting condition will be established. These computational study, on one hand, can bridge the gap between experimental observations and theoretical predictions. On the other hand, it can provide direct scientific foundation to designing novel polymer nano-materials.

纳米粒子增强聚合物复合材料是当今高分子科学中的一个重要研究领域，具有十分重要的科学价值和工业应用前景。实现聚合物基纳米复合材料优异性能的关键是使纳米粒子在聚合物基质中形成均匀稳定的分散，这就要求从分子水平上理解纳米粒子-聚合物界面层的微观相行为，揭示纳米尺寸下粒子表面及聚合物分子特性影响界面结合及分散状态的物理机制。本项目申请借助Monte Carlo和Molecular Dynamics模拟方法，结合统计热力学理论，通过建立合理有效的理论模型，研究纳米粒子表面性质（作用位点分布和表面粗糙度）、分子量多分散性以及分子链刚性对纳米粒子-聚合物界面相容性的影响，建立界面层微观结构和动力学行为与粒径、聚合物分子量和界面作用强度之间的定量关系。通过综合模拟结果，一方面可以更好地弥合实验发现与理论预测两种手段之间的鸿沟，另一方面可以为设计预测新型聚合物基纳米复合材料提供直接的理论依据。

高分子基纳米复合材料是一类典型的多相多组分热力学体系，微尺度相区之间的纳米复合赋予了固相宏观材料以多相互补的独特性能，因而在工业和民用消费领域都获得了非常广泛的应用。科学家们致力于使用具有不同化学结构的纳米填料和高分子基体材料，制备了大量的满足特定场景需求的高性能复合材料。尽管如此，基于目标性能需求而进行的复合材料分子设计及加工制备仍然是一项具有相当挑战性的课题。本项目在常规的高分子弹性体复合材料固相混炼加工的基础上，从乳液出发，采用湿法预分散首先制备预混胶的新思路，成功地制备了一系列力学性能显著增强的高分子基纳米复合材料。同时，发展了系列理论计算工具对于实验体系进行模拟计算，以期对纳米填料及基体结构特性在材料形变过程中的力学增强机制进行定量系统的阐释。本项目所取得的阶段性成果能够为具备多层级凝聚态结构的高分子纳米复合材料的普适性制备和加工规律的深入探索研究提供科学指导和理论支撑。