结构可控聚合物接枝纳米颗粒及其复合材料流变学

In this project, we will prepare serials of tailor-designed polymer-grafted nanoparticles (PGNPs) with different microstructures (i.e., geometry of core, length of grafted chains, density of grafted chains, and size of core) in controlled manner utilizing the method of self-/co-assembling of block copolymers. The so-called “completely miscible” polymer composites will be obtained by evenly dispersing the PGNPs with the controlled grafted length and density in the polymer matrix that same to the grafted chains. This will provide a good model system for the studies on the rheological properties of polymer nanocomposites. The research will focus on the influences of the shape transformation of PGNPs (from sphere to cylinder, and to lamellae) as well as the polymer bridge effects between the grafted chains and those of polymer matrix. Based on the studies on model PGNOs filled polymer composites, we will construct the systematic knowledge about the PGNPs’ structure-dispersing state-rheological property relationships, along with the general dispersing phase diagram about the PGNPs and the equations describing the flowing behaviors of the model composites. In the application area, by utilizing the shape effects of PGNPs and the polymer bridging effects between the grafted and free polymer chains, we expect to fabricate the polymer nanocomposites with high mechanical performances but low nanoparticles content.

本项目利用其中一段侧链含有烷基氧化硅烷的两嵌段共聚物进行自组装或共组装，水解交联后制备刚性内核的聚合物接枝纳米颗粒。通过调节嵌段共聚物长度和比例、共组装齐聚物含量，可精确调控纳米颗粒的内核形状、接枝链长度、接枝密度、内核尺寸等结构参数。利用小角X射线散射和激光光散射、稀溶液流变学、电镜观察和热失重等表征手段，确定聚合物接枝纳米颗粒的结构参数。当接枝链密度和长度满足一定条件，纳米颗粒可以在相同化学结构的基体聚合物中均匀分散，形成所谓的“完全相容性”聚合物纳米复合材料。重点聚焦于纳米颗粒形状效应和接枝链桥连作用这两个重要基本问题，阐明这类材料的结构-加工分散-流变性能之间的关系，期望建立更为普适的纳米复合体系的分散相图，复合体系粘弹性能的微观机理，以及自由链和接枝链的松弛机理。在材料的开发方面，将利用纳米颗粒形状效应和聚合物桥连效应，制备低纳米填料含量、高性能的新型聚合物纳米复合材料。

本项目按照“资助项目计划书”内容执行，从基础研究和材料开发两个方面开展结构可控聚合物接枝纳米颗粒（PGNPs）及其复合材料的相关研究。在聚合物接枝纳米颗粒制备与表征方面，发展完善了PGNPs制备平台技术，合成系列不同种类聚合物接枝的PGNPs、接枝链长度双分布PGNPs、双组分PGNPs，嵌段共聚物PGNPs。该方法的最大优势是可以制备高分子量接枝链，其分子量远高于传统的固相表面接枝方法。开展PGNPs溶液流变学研究，揭示了该类软胶体体系液体-固体转变的物理本质，为控制这类纳米复合体系的流动性质提供了理论基础。通过熔体相容性共混熔体流变学研究，建立了PGNPs相容性纳米复合体系弹性网络的逾渗模型。最后在PGNPs弹性体材料和增强增韧方向取得一些突破性认识。