含离子的介电非均一性高分子液体体系平衡态性质与动力学行为的分子动力学模拟研究

Ion-doped polymer solution plays an important role in application of material preparation and designing electrochemical devices. The two key ingredients that influence properties of system are the dielectric contrast between components in the system and variation of dielectric function near ion. Conventional theory and simulation fail to describe dielectric inhomogeneity from the molecular level, which hinder researchers from studying the effects of dielectric inhomogeneity on the dynamics of system. Our objective is to develop molecular dynamics simulation method to study the dynamic behavior of the dielectric inhomogeneous ion-containing polymer solution. We will investigate the physical mechanism of effects of the reorganization of dipoles around ions on the equilibrium properties of ion-containing homopolymer solution, block copolymer solution and ionic liquids, to reveal the importance of the solvation energy of ion in the phase behavior of homopolymer blend solution and block copolymer solution. Then, we will study the physical essence of the role of dielectric contrast between components plays in the dynamical behavior of system, clarify the micromechanism of coupling effects between flow field and solvation energy on the chain conformation. Based on these results, we will reveal the correlation between dynamical behavior of polymer chain and external factors, such as chain length, ion concentration, valence of ion and strength of flow field, which can be benefit for the experiments studies and provides simulation and theory guidance for designing devices.

离子掺杂的高分子液体体系在材料制备和电化学器件设计方面具有重要的应用，组分间介电差异以及离子周围介电函数变化是影响体系性质的核心问题，传统的理论与模拟研究难以从分子水平描述体系介电非均一性，无法考察介电非均一性对体系动力学行为的影响。本项目借助构建可用于研究介电非均一性体系性质的分子动力学模拟方法，考察离子周围的偶极子重组效应对含有离子的高分子溶液均聚物体系、嵌段共聚物溶液体系和离子液体体系平衡态性质的影响机理，揭示离子的溶剂化作用在均聚物共混体系以及嵌段共聚物体系相行为中所起的作用，探索组分间介电差异对体系动力学行为影响的物理本质，明晰流场和离子溶剂化耦合作用对高分子链构象影响的微观机制，揭示链长、离子浓度、离子价态以及外场强度等因素对高分子链动力学行为的影响规律，为相关的实验研究及器件设计提供模拟依据和理论指导。

本项目构建并发展了可用于研究介电非均一性体系性质的分子动力学模拟方法，并结合多粒子碰撞动力学模拟方法，针对离子掺杂的高分子溶液体系和聚电解质溶液体系的构象性质和动力学行为进行模拟研究，阐述了高分子的链接性、链长以及拓扑结构等因素对高分子体系内离子溶剂化能的影响，揭示了离子周围偶极子重组效应是影响体系相形为的关键因素。我们的研究明晰了静电作用、流体力学作用以及外场强度等因素对聚电解质构象行为和动力学行为的影响，发现随着静电相互作用的增强，聚电解质发生了复杂的形状变化。当不考虑流体力学相互作用时，链的扩散系数展现几乎单调变化的行为；而当考虑流体力学相互作用后，链的扩散系数展现出现先减小后增加的变化行为。揭示剪切流会将反离子从链骨架上剥离，导致链周围束缚的反离子数目减少，进而影响高分子链的构象、取向和动力学行为。我们的研究结果澄清了对聚电解质扩散行为的一些争议，从分子水平明晰了粒子间静电作用、长程流体力学作用以及外场耦合作用是影响聚电解质构象变化和动力学行为的关键因素，为相关的实验研究及器件设计提供模拟依据和理论指导。