嵌段共聚物自组装多孔形态的形成机理研究

Porous nanostructures have attracted much scientific attention because of their potential applications. Several methods have been developed for the preparation of block copolymer porous structures. However, the formation mechanism of porous structures is not quite clear. In this proposal, we will investigate the formation mechanism of porous block copolymer membranes and porous nanoparticles using molecular simulations including Monte Carlo, simulated annealing, molecular dynamics. For porous block copolymer membranes, we will concentrate on these formed by diblock copolymers, triblock terpolymers and mixture of two triblock terpolymers through the self-assembly and non-solvent-induced phase separation process. We will examine the effect of the types, compositon and concentration of the block copolymers, the property of the organic solvent, the degree of the solvent evaporation, the property of the non-solvent on the self-assembld morphologies and porous structures. For porous particles, we will concentrate on these fabricated by tuning the interfacial behavior of diblock copolymer and triblock terpolymer droplets in oil-in-water emulsions. We will examine the effect of the property and content of the surfactant, copolymer composition and concentration on the self-assembled morphologies and porous structures. We will find out the conditions for the formation of different morphologies, especially the conditions for the formation of porous moephologies. We will construct the phase diagrams as a function of different parameters for the two types of systems. Based on the above studies, we will illucidate the formation mechanism of the self-assembled morphologies, especially porous morphologies. Furthermore, we will sum up the generic characteristic of the variations of the self-assembled morphologies, and predict and design the self-assembly system of the block copolymer with specific porous morphologies. The results of this study will provide an insight into the porous morphologies of block copolymers. The self-assembly rules obtained from this study will provide theoretical guidance for the application of the self-assembled block copolymers as ultrafiltration materials.

多孔纳米结构因具有重要的应用前景而备受关注。已经开发了一些制备嵌段共聚物多孔纳米结构的方法，然而其形成机理还不是十分清楚。本项目拟采用分子模拟方法，围绕嵌段共聚物多孔膜和多孔纳米粒子体系中多孔形态的形成机理开展研究。对前者主要针对嵌段共聚物通过自组装与非溶剂诱导相分离过程成膜体系；考察共聚物的类型、组成成分和浓度、有机溶剂的性质、溶剂的蒸发、和非溶剂的性质等对自组装形态的影响。对后者主要针对嵌段共聚物水包油乳液液滴体系；考察表面活性剂的性质与含量、共聚物的组成成分、浓度等对所生成的粒子的形态及孔结构的影响。探索体系形成不同形态的条件，特别是形成多孔形态的条件。获取两类体系自组装形态随不同参数演化的相图。进而归纳、总结每类体系自组装形态的形成机制；并进一步预言和设计具有特定多孔形态的嵌段共聚物自组装体系。从本研究获取的自组装规律将对嵌段共聚物作为诸如超滤材料等的技术应用提供理论指导。

在本项目的资助下，项目组成员使用Monte Carlo、模拟退火等分子模拟方法以及自洽场理论计算，围绕嵌段共聚物自组装多孔膜和多孔纳米粒子体系中多孔形态的形成机理开展研究。通过系统地改变体系中的相互作用（包括不同嵌段之间的、每一嵌段与不同机溶剂(或与平板)之间的、以及不同溶剂分子之间的相互作用）、嵌段共聚物类型和组成，对两嵌段共聚物、ABA三嵌段共聚物、以及ABC三嵌段共聚物体系在油/水乳化液滴中以及在两平行板间的自组装行为做了系统研究；获得了体系自组装形态及其孔结构随不同相互作用参数演化的相图、以及随嵌段共聚物类型和组成演化的相图。总结、归纳了上述参数对自组装形态及孔结构的调控规律以及自组装形态的形成机制。另外，对非手性嵌段共聚物因受限诱导而形成的螺旋结构的手性和股数调控、聚合物自组装形成的含有面内晶序的囊泡中的拓扑缺陷、周期盒子中六角柱状相的周期和序参量、溶剂对嵌段共聚物/均聚物共混体系增容以及两种嵌段共聚物共混物在选择性溶剂中的自组装行为等进行了系统研究。相关研究成果将为对嵌段共聚物作为诸如超滤材料等技术应用提供理论指导。