基于粒子拓扑形状、粒子与聚合物间相互作用协同调控聚合物亚浓溶液流变行为及其在复合功能材料制备中的应用

Viscosity reduction of polymer semidilute solution has been a knot in the material preparation fields, while the introduction of functional particles could always lead to a further increase of the solution viscosity..For example, many polymer semidilute solution are used for electrospinning functional nanofibers. However, most of them exhibit narrow spinnable concentration window, which makes them an unfavorable system for electrospinning and the fibrous morphology might be difficult to tune. To achieve versatility, some inorganic fillers are added into the electrospinning solutions, however, these particles often lead to high viscosity and bad electrospinnability. To explore the influence of particle topological shape on the rheological behavior of polyvinyl alcohol (PVA) aqueous solution, we have synthesized three kinds of layered double hydroxides (LDH) (nanosized layered crystals, microsized layered crystals and nanoscrolls). Combined theoretical calculation with dynamic mechanical analysis, the adsorbed state of PVA chains on surface of the three LDH particles was proposed, in which PVA chains exhibited various adsorbed state due to different interaction between PVA chains and LDH particles with disparate topological shape. PVA chains could prefer to wind around the LDH nanoscrolls rather than participate in constructing global H-bonding network at a certain loading and thus make the viscosity of the composite suspension lower than that of pure PVA solution, which is also different from that of the other two traditional LDH platelets. Accordingly, one-dimensional LDH nanoscrolls could act as a viscosity modulator. A small amount of LDH nanoscrolls could be used as a thicker for semidilute PVA solution while 2.0wt% LDH nanoscrolls as a thinner. LDH nanoscrolls were introduced into PVA solution to broaden effectively its electrospinnable concentration window from 8.5~11.3wt% to 6.5~18.0wt%. More importantly, the obtained composite nanofibers exhibited outstanding adsorption capacity for methyl orange in wastewater and their removal efficiency was maintained even after three regeneration cycles. .Based on the above results, we thought that the rheological behavior of polymer semidilute solution could be controlled by the topological shape of particles cooperating with the interaction between polymer and particles. Conducted by this idea, the functional nanoparticles (inorganic, organic and metal particles) with various surface characters (polar, nonpolar and others with functional groups) and topological shapes (zero-dimension, one-dimension and two-dimension) will be prepared in this project, and then are introduced into the polymer semidilute aqueous or nonaqueous solution through in-situ, conventional and reversed charging method, respectively. By this way, the relationship between the interaction of macromolecule-nanoparticle, the topological shape of particles and rheological behavior of polymer solution will be explored, and then the condition of coordinated reducing viscosity between the topological shape of particles and the interaction of macromolecule-nanoparticle will be confirmed. The advantage of using particles to decrease the viscosity of semidilute solution and control the rheological behavior is that not only the operation window of polymer semidilute solution and preparation technology could be optimized, but also the regulative space for broadening morphology structure and function of the composite materials would be greatly increased. The controlling condition of rheological behavior by means of introducing particles, especially for the mechanism of viscosity reduction could be revealed through the investigation in this project. Therefore, research of the present project has far-reaching academic and practical significance, and will provide a new approach and theoretical basis for function optimization of the composite materials, as well as technological innovation of polymer solution processing.

聚合物亚浓溶液的降黏一直是材料制备业的难题，与功能性粒子的复合又使溶液黏度进一步增大。本申请以粒子拓扑形状及其与聚合物间相互作用可协同调控聚合物亚浓溶液流变行为为指导思想，拟将具有不同拓扑形状（0维、1维、2维）及表面性质（极性、非极性、功能基团等）的功能粒子（无机粒子、有机粒子、金属粒子等）以不同方法（原位制备、常规混合、反向混合等）添加到聚合物亚浓水溶液及非水溶液中，考察溶液中大分子形态结构及流变行为的变化规律，确定粒子拓扑形状及其与聚合物间相互作用的协同条件，仅通过粒子实现对亚浓溶液的降黏及流变行为调控，其优势在于增大聚合物溶液可操作浓度窗口，优化材料制备工艺的同时，可大大拓宽材料形态结构及性能的调控空间。通过研究，揭示粒子调控流变行为，特别是粒子降黏的机理，可为复合功能材料的制备及性能优化，甚至为聚合物溶液加工工艺的优化提供新的途径和理论依据，具有重要的理论意义及实际价值。

聚合物亚浓溶液的流变行为调控一直是材料制备业的难题，功能性粒子的加入常使溶液黏度进一步增大。该项目基于粒子拓扑形状及其与聚合物间相互作用，协同调控聚合物亚浓溶液的流变行为，探讨粒子调控可操作浓度窗口的可行性，并将其应用于复合功能材料的制备。通过研究具有不同拓扑形状及表面性质的粒子对聚合物溶液流变行为的影响，确定0维纳米粒子（层状双金属氢氧化物LDH纳米片、炭黑等）在聚合物（水）溶液中主要起增黏作用，而1维粒子（LDH纳米卷、CNTs等）和2维粒子（LDH微米片、石墨烯等）在一定用量下均可使复合溶液黏度降低。通过低浓度加0维粒子以增黏，高浓度加1维粒子以降黏的手段，可拓宽聚合物溶液的静电纺丝窗口。发现聚乙烯醇PVA/CNTs复合溶液的黏度随CNTs用量增加呈“N”型变化趋势，出现两个拐点。低用量拐点处，CNTs主要起物理交联点作用，体系黏度增加；高用量拐点处，CNTs对PVA分子间氢键作用破坏最为严重，体系黏度低于纯PVA溶液。CNTs与PVA大分子间相互作用越强，降黏效果越显著。通过加入CNTs调控PVA水溶液流变行为、优化旋涂工艺、引入泡孔及交联结构，制备出响应时间短、灵敏的聚合物基湿敏膜。通过改变电解液的流变行为（聚合物种类、分子量、浓度等）调控电化学沉积过程，获得了具有不同形貌的LDH粒子，得益于独特的多级结构和高比表面积，制备的LDH电极材料具有更高的比电容和更长的循环寿命。通过调控粒子与基体间相互作用，制备了聚苯胺/NiCo-LDH纳米卷复合电极,该电极比电容高，倍率性能优异，循环寿命长。.以上研究结果丰富了高分子流变学关于粒子拓扑形状、粒子表面性质等对高分子溶液黏弹行为影响的相关理论，揭示了粒子调控高分子溶液流变行为的机理，反之，又利用高分子溶液调控粒子的生长，优化结构与性能；基于上述理论研究，制备的湿度传感器和超级电容器两类功能复合材料。以上研究结果为聚合物/粒子复合材料功能优化及结构设计提供了理论指导和新途径。