大孔取向、多级孔结构高分子纳米纤维气凝胶的可控构筑及其空气过滤性能研究

The application of 2D polymer nanofiber membranes current face an awkward question, filtration efficiency and pressure drop synchronize increase or decrease. Moreover, low dust containing capacity is another big problem. To address these key issues, this project intends to develop a simple, efficient, and green approach for preparing novel polymer nanofiber aerogels with macro oriented hierarchical porous structures. In this project, polymer nanofiber aerogels with controllable hierarchical porous structures (e.g., macro, mesoporous, micro structures) are prepared by simultaneously utilizing renewable biomass resource, lignin or poly(amic acid) with abundant functional groups as elementary materials, playing as cross-linker, pore-forming agent, as well as reinforcing filler, electrospinning polymer nanofibers as main materials, via oriented ice template method and plasma technology. The oriented ice template, physical and chemical interactions between elementary materials and polymer nanofibers, and post-processing approaches (such as plasma treatment) will be well investigated to reveal the formation mechanism of macro oriented hierarchical porous structures. With these designed porous structures and surface modification, the filtration performances, such as filtration efficiency, pressure drop, and dust containing capacity will be improved. Furthermore, the relationship among the structures, the surface properties, and the filtration performances of the as-prepared macro oriented hierarchical porous polymer nanofiber aerogels will be intensely explored, providing theoretical and practical foundations for controllable fabrication and wide application of polymer nanofiber aerogels with high filtration performance in cleaning air filed.

开发性能优异的空气过滤材料对有效治理空气污染、提高空气质量具有重要意义。针对目前纤维膜材料在空气过滤中存在的高过滤效率和低阻力压降无法兼得且低容尘量等关键科学问题，本项目基于申请人在高分子基复合气凝胶的研究基础上，提出一种简单、高效和绿色制备高分子纳米纤维复合气凝胶的新方法。以富含可反应官能团的生物质木质素或者合成高分子如聚酰胺酸为构筑基元，以静电纺高分子纳米纤维为构筑基体，利用构筑基元与构筑基体之间的物理或化学相互作用以及定向冷冻技术，可控构筑出具有大孔取向、多级孔结构的高分子纳米纤维复合气凝胶。通过对纳米纤维气凝胶的多级孔结构与表/界面性质的可控调节，实现其在空气过滤应用中的过滤效率、阻力压降和容尘量等性能的全面优化。深入研究及建立此类高分子纳米纤维气凝胶材料的结构和表/界面性质与空气过滤性能之间的关系规律，为新型高性能空气过滤材料的可控制备和应用奠定理论基础。

本项目围绕构筑大孔取向、多级孔结构高分子纳米纤维复合气凝胶方面开展了深入系统的研究工作，自主设计了定向冰晶诱导自组装装置，提出了一种简单、高效和绿色制备的工艺方法。主要研究成果包括：（1）氧等离子体处理技术在构筑聚酰亚胺（PI）-聚酰胺酸（PAA）/聚丙烯腈纳米纤维复合多级孔材料及在调控表/界面性质方面的应用。研究表明氧等离子体可实现纤维表面改性、微纳孔结构构筑以及实现部分PAA亚酰胺化。所获得的最佳复合多孔材料对PM 0.3、PM 0.5和PM 1都具有很高的过滤效率（≥99.72%）和低阻力压降性能，实现高过滤效率、低阻力压降的研究预期。（2）以预氧化静电纺聚丙烯腈（OPAN）纳米纤维为构筑基体材料，以水溶性PAA为粘结剂和交联剂，通过定向冷冻技术和热亚酰胺化，构筑出大孔取向、多级孔结构OPAN/PI纳米纤维复合气凝胶。通过控制PAA用量，可实现孔结构和表/界面性质的可控调节。该复合气凝胶具有很好的有机污染物吸附性能。（3）大孔取向、多级孔结构高分子基复合气凝胶在导热材料领域中的探索：以水溶性PAA为粘结剂和交联剂，银纳米线（Ag NW）为构筑基体，制备出大孔取向、多级孔结构Ag NW/PAA复合气凝胶。以之为三维导热网络，与环氧树脂（EP）复合，在Ag NWs 1.07 vol%时，Ag NW/PAA@EP的热导率为1.227 W m-1 k-1，实现低导热填料用量、高热导率的效果，拓宽了高分子基纳米复合气凝胶的应用领域。本项目的实施，为大孔取向、多级孔结构的高分子基纳米复合气凝胶的研发及其潜在应用研究提供了理论和实践基础。