POSS分子表面迁移机制的研究与聚酰胺/POSS纳米复合材料表面微观结构的调控

Surface structural design and surface performance tunability are current and difficult topics in developing high performance polymeric materials. In this application, polyhedral oligomeric silsesquioxanes (POSS), which has shown apparent surface migration characteristics, is to be used as nanofiller to prepare polycaprolactam (PA6)/POSS nanocomposite membranes through the solution blending method. By adjusting the POSS structure and phase separation process of the solution, and combined with the effect of a flat electric field, it is possible to control the migration of POSS molecules during the membrane-forming proces. Such a process would promote the surface segregation of POSS, leading eventually to a nanocomposite membrane that is completely covered by a layer of POSS on the outermost surface and having a gradient distribution of POSS within the membrane. Based on this membrane preparation process, the surface migration mechanism of POSS, the influence of POSS on the crystallization process of PA6, the microphase miscibility mechanism of PA6 and POSS interface and the surface migration behavior of POSS under the coordinating effects of electric field and the solution phase separation mechanism will be studied. A model to relate the processing conditions, POSS molecular structure, POSS surface migration characteristics and membrane surface properties will be established. From this model, an "active" process to enhance polymer nanocomposite surfaces based on the mobility of inorganic nanoparticles will be developed, ultimately contributing to polymer nanocomposite surface design theory.

材料表面的结构设计及性能调控是高分子材料高性能化的研究热点及难点。本申请拟选用具有明显表面迁移特性的多面齐聚倍半硅氧烷（POSS）为纳米填料，经溶液共混法，制备聚已内酰胺（PA6）/POSS纳米复合膜。通过调节POSS的分子结构和溶液相分离过程，结合平板电场作用，控制成膜过程中POSS的运动行为，强化POSS在PA6表面的离析程度，由此获得表面完全由POSS层覆盖、内部POSS呈梯度化分布的复合材料。并以该纳米复合膜制备过程为对象，研究POSS表面迁移机理、POSS对PA6结晶过程的影响、POSS与PA6链段间的微相混合机理以及电场环境与溶液相分离机制协同作用下POSS的表面迁移行为。建立POSS分子设计、成膜工艺、POSS表面迁移程度以及材料表面性能间的定量关系模型，最终提出一条以充分利用无机纳米粒子运动性为特征的"主动式"纳米复合材料表面强化技术，丰富高分子纳米复合材料表面设计理论。

材料表、界面的结构设计是高分子材料高性能化过程中重要的基础科学问题。本项目基于“利用电场环境与溶液相分离机制的协同作用，强化POSS在复合膜成型过程中的表面迁移行为，设计POSS在聚合物表面及内部的分散形式”的研究思想，提出一条制备表面强化型聚合物/POSS纳米复合材料的新思路。以典型的聚酰胺材料——聚己内酰胺（PA6）为基体，通过改变纳米填料的空间结构和化学组成，并结合平板电场研究纳米填料在电场辅助相转化法制备PA6复合膜过程中的表面迁移机理、建立了定量表征PA6氢键取向的方法、探析了电场辅助下的溶液相分离机理，详细表征了电场作用下复合膜的聚集态结构，并研究了纳米粒子表面迁移行为对复合膜表、界面结构和性能的影响。最后将研究结果拓展到PA6与壳聚糖共混体系和聚乙烯复合材料等领域。通过调节纳米填料的表面迁移行为，能够大幅提升共混物的力学性能和表面性质。电场力诱导了铸膜液体系内的偶极子取向，增强了填料与链段的相互作用，抑制了纳米填料的表面迁移行为，能够获得三维空间上均匀分布的纳米填料。电场力诱导的溶液相分离过程能够使得PA6表面从超亲水变为超疏水， PA6的结晶程度大幅下降，达40%。