基于冷冻干燥技术制备的PI气凝胶微观形态形成机理，调控及其应用研究

Owning to low dielectric constant, excellent mechanical strength, dimensional stability and extreme high/low temperature performance, aromatic polyimide aerogels (PI aerogels) with rigid aromatic heterocyclic structure have showed great value and prospect to apply in aerospace, microelectronics and other high-tech fields. Based on the principle of freeze drying technology, this project studies and optimizes systematically freeze drying process conditions by choosing green water soluble poly amic acid salt (PAAS) with high molecular weight as raw material. From the components of the chemical structure and interaction of the system of freeze drying process, the relationship of PI aerogels between micromorphology and correlative factors including freeze drying process conditions, design and matching of solvent and polymer chemical structure and their intermolecular interaction type, are researched systematically. Based on the relationship between solvent crystallization process and phase separation, the formation mechanism and control methods of PI aerogels micromorphology are established furtherly. Understanding the relationship of chemical structure, microstructure and properties deeply, the preparing method of PI aerogels with excellent comprehensive performance is built. Furthermore, due to special microstructure and properties of PI aerogels fabricated by freeze drying method, the application of this high performance PI aerogel are studied in these fields, such as heat insulation, high elastic materials, and sensors. Through above researches, this project will achieve with environmental protection, high efficiency and low cost in PI aerogels fabrication, and provide theoretical and technical basis for their further development.

芳香族聚酰亚胺气凝胶（ PI aerogels）由于在PI主链中含有大量刚性的芳杂环结构，具有低介电常数、优异的机械强度、良好的尺寸稳定性以及耐高 低温等性能，在微电子，航空航天等高新技术领域具有极大的应用价值和前景。本项目采用具有高分子量水溶性PAAS作为PI前驱体，通过冷冻干燥技术制备PI气凝胶。从各组分化学结构和相互作用出发，系统研究冷冻干燥技术工艺条件，冻干剂组分化学结构设计和匹配，聚合物化学结构和分子间相互作用类型等与气凝胶微观形态的相互关系，提出PI气凝胶微观形态形成机理和微观形态的调控机制，明确化学结构，微观形态和性能之间的相互关系，制备综合性能优异的PI气凝胶。并以特定微观形态或性能为基础，拓展研究PI气凝胶新的应用领域。拟通过以上研究，实现绿色环保，高效，低成本制备具有综合性能优势的PI气凝胶，并为其进一步拓展应用领域提供技术依据和理论指导。

聚酰亚胺（PI）气凝胶因具有优异的机械性能、热稳定性能和环境稳定性等特点，使其在航空航天、环保、微电子等领域具有良好的应用前景。本项目以聚酰亚胺气凝胶微观形态形成和调控机制为核心的基础科学问题出发，重点研究了聚酰亚胺气凝胶微观形态形成与相关因素之间的关联性,建立微观形态调控机制以及功能性组分-微观形态-功能性之间的构效关系等关键科学问题。项目的主要研究包括：（1）通过研究溶剂组成及工艺成功实现了聚酰亚胺气凝胶微观形态调控，利用该气凝胶高弹性及多层次孔结构特点，制备了高灵敏性的压力传感器。（2）通过冷冻工艺设计制备得到了一系列微观结构有序的，各向异性的聚酰亚胺及复合气凝胶。利用针状和层状结构的特点，分别与CNT和rGO复合制备了针状结构和层状结构的复合气凝胶，并探索了在电磁屏蔽材料和柔性压力传感器领域的应用。（3）将苯并咪唑结构和由直接氟化技术制备的高接枝率的氨基官能化碳纳米管引入到聚酰亚胺气凝胶中，设计并制备了有效交联结构，成功解决了聚酰亚胺气凝胶制备中收缩率大、微观形态不可控和机械强度差等问题。并在高效油水分离应用中展示出了非常好的效果。（4）通过SOL-GEL和物理相互作用构建凝胶骨架，实现了非化学交联聚酰亚胺基碳气凝胶微观结构构建、制备及电化学应用。（5）采用冻干剂作为合成聚酰胺酸的溶剂，实现在冻干过程中溶剂的直接去除，成功开发了聚酰亚胺气凝胶制备新方法。该方法避免了溶剂置换等多步繁杂过程，使制备聚酰亚胺气凝胶流程大大缩短。本项目的研究工作按照计划进行了实施，全面达成了预期的研究目标，取得了系列原创新研究成果。