NASA Glenn Research Center , 21000 Brookpark Road, Cleveland, Ohio 44135, United States.
ACS Appl Mater Interfaces. 2015 Jan 21;7(2):1240-9. doi: 10.1021/am507268c. Epub 2015 Jan 7.
Polyimide aerogels combine high porosity, low thermal conductivity, flexibility, and low density with excellent mechanical properties. However, previously used cross-linkers, such as 1,3,5-triaminophenoxybenzene (TAB), 2,4,6-tris(4-aminophenyl)pyridine (TAPP), or octa(aminophenoxy)silsesquioxane (OAPS), either are not commercially available or are prohibitively expensive. Finding more cost efficient cross-linkers that are commercially available to synthesize these aerogels is crucial for making large scale manufacturing attractive. Herein, we describe an approach to making polyimide aerogels starting with amine capped oligomers that are cross-linked with 1,3,5-benzenetricarbonyl trichloride (BTC). BTC is a lower cost, commercially available alternative to TAB, TAPP, or OAPS. Aerogels made in this way have the same or higher modulus and higher surface area compared to those previously reported with either TAB or OAPS cross-links at the same density. While the cross-link structure is an amide, the thermal stability is not compromised most likely because the cross-link is only a small part of the composition of the aerogel. Onset of decomposition depends primarily on the backbone chemistry with 4,4'-oxidianiline (ODA) being more thermally stable than 2,2'-dimethylbenzidine (DMBZ), similar to those previously reported with other cross-links.
聚酰亚胺气凝胶具有高孔隙率、低热导率、柔韧性和低密度的特点，同时还具有优异的机械性能。然而，以前使用的交联剂，如 1,3,5-三氨基苯氧基苯（TAB）、2,4,6-三（4-氨基苯基）吡啶（TAPP）或八（氨基苯氧基）倍半硅氧烷（OAPS），要么不是商业上可获得的，要么价格过高。寻找更具成本效益且商业上可获得的交联剂来合成这些气凝胶对于实现大规模制造具有吸引力至关重要。在此，我们描述了一种使用胺封端的低聚物制备聚酰亚胺气凝胶的方法，该低聚物通过 1,3,5-苯三甲酰氯（BTC）交联。BTC 是 TAB、TAPP 或 OAPS 的低成本、商业上可获得的替代品。用这种方法制备的气凝胶与以前用 TAB 或 OAPS 交联剂在相同密度下制备的气凝胶具有相同或更高的模量和更高的比表面积。虽然交联结构是酰胺，但热稳定性没有受到影响，这很可能是因为交联只是气凝胶组成的一小部分。分解起始取决于主链化学，4,4'-氧化二苯胺（ODA）比 2,2'-二甲基联苯胺（DMBZ）更热稳定，这与以前用其他交联剂报道的情况类似。
