全有机PVDF/含醚基PI介电材料设计、制备及结构与性能调控

Polymer dielectrics with high energy density is the key to the development of the next-generation capacitors with high energy storage. Compared with the state-of-the-art biaxially oriented polypropylene (BOPP) dielectrics, fluoropolymers, such as poly(vinylidene fluoride) [PVDF] and its copolymers and terpolymers, have a much higher energy density than BOPP due to their high dielectric constant. However, the high dielectric loss (about 30%) at high electric field caused by field-induced switching of ferroelectric domain has severely limited practical application of PVDF based polymers. In this program, by taking advantage of molecular structure design of materials, a new approach to significantly suppress the existence and switching of domain walls via multi-scale manipulation of microstructure of PVDF was proposed. In detail, polyether-containing polyimide (PI) will be used for the molecular level modification of PVDF by a blending method. Based on the in-depth investigation on intermolecular interaction between PVDF and PI and condensed structure of the composite, the approach to manipulate material's microstructure by polymer blending will be provided, and the relationship between microstructure of the composite and macro dielectric and energy storage properties will be revealed, which will lay foundation for the practical application of PVDF based polymer dielectrics.

高储能密度聚合物介质材料是发展下一代高储能电容器的关键。与常用双轴拉伸聚丙烯(BOPP)相比，含氟聚合物如聚偏氟乙烯(PVDF)及其二元和三元共聚物由于其高介电常数的特点，使其具有远高于BOPP的储能密度。但PVDF类材料在电场存在下内部铁电畴翻转带来的高介电损耗(~30%)缺点限制了这类材料的应用。本项目针对PVDF材料介电损耗高的缺点，提出利用材料分子结构设计的思想，对PVDF材料结构进行多尺度调控，实现显著抑制铁电畴的存在和翻转。具体采用具有不同分子结构的含醚基聚酰亚胺(PI)对PVDF进行分子尺度的掺杂改性，深入研究PVDF与PI分子间的相互作用及复合材料的聚集态结构，提出通过聚合物掺杂复合调控材料微观结构的方法，揭示复合材料微观结构与介电性能和储能特性的关系，为这类材料的应用奠定基础。

高储能密度聚合物电介质材料是发展下一代高储能电容器的关键。与高介电无机纳米粒子复合是提高聚合物电介质材料储能密度的常见方法，但是高的填充在提高介电常数的同时会使得机械性能、击穿强度和能量密度下降。本项目以聚醚酰亚胺（PEI）和聚偏氟乙烯（PVDF）为基体，以纳米钛酸钡颗粒（BT NPs）和氮化硼纳米薄片（BNNS）为填料，研究了无机粒子的低含量填充对聚合物介电储能性能的影响并利用COMSOL多物理场模拟初步探索了低含量填充对复合材料击穿场强的影响机制。研究发现无机粒子的低含量填充可以降低复合材料内部电场的畸变程度和抑制电树的发展，实现了介电常数和击穿场强的同时提高，进而实现了聚合物基电介质材料储能密度的提高。低含量无机纳米粒子填充为新一代高储能密度聚合物电介质材料的开发和应用提供了新的思路。