冷冻干燥制备聚甲基丙烯酰亚胺气凝胶及其微观形态的调控

Preparation of Polymethacryloimide Aerogels by Freeze-drying and Regulation of Their Micro-morphology

由自由基溶液聚合制备丙烯腈(AN)/甲基丙烯酸(MAA)共聚物,随后使用三乙胺(TEA)对共聚物进行水性处理,得到水溶性的MAA/AN共聚物季铵盐。将不同浓度的水溶性MAA/AN共聚物季铵盐溶液先通过冷冻干燥法制备MAA/AN共聚物季铵盐气凝胶,再经过热酰亚胺化得到聚甲基丙烯酰亚胺(PMI)气凝胶。通过调控季铵盐溶液固含量和冻干溶剂的组成,成功实现了对PMI气凝胶微观形态的调控。研究发现,以纯水作为冻干溶剂,得到孔径为14μm左右的奶酪状孔洞结构,随着固含量的增加,孔壁增厚,压缩性能增强。以叔丁醇替代部分水作为冻干剂,随着叔丁醇含量增加,孔洞尺寸先减小后增加,在水和叔丁醇共晶点附近孔洞尺寸最小。并且叔丁醇的加入有效的降低了气凝胶的密度和收缩率,分别低至0.0785 g/cm^(3)和27.47%。

Acrylonitrile(AN)/methacrylic acid(MAA)copolymer was prepared by free-radical solution polymerization,and then water-soluble MAA/AN copolymer quaternary ammonium salt was obtained by treating the copolymer with triethylamine(TEA).MAA/AN copolymer quaternary ammonium salt aerogel was prepared by freeze-drying with a certain concentration of water-soluble MAA/AN copolymer quaternary ammonium salt solution,after that polymethylacryloimide(PMI)aerogel was obtained by thermal imidization.By controlling the solid content of quaternary ammonium salt solution and the composition of freeze-dried solvent,the micro-morphology of PMI aerogel was successfully controlled.It is found that cheese-like pore structure with pore size of 14μm is obtained by using pure water as freeze-drying solvent.With the increase of solid content,the pore wall became thicker and the compression performance increase.As the content of tert-butanol(TBA)increases,the pore size first decreases and then increases,and the pore size is the smallest near the eutectic point of water and TBA.The fabricated aerogels present density and shrinkage,as low as 0.0785 g/cm^(3) and 27.47%,respectively.