Low shrinkage, mechanically strong polyimide hybrid aerogels containing hollow mesoporous silica nanospheres

Abstract

Low shrinkage, mechanically-strong polyimide hybrid aerogels were synthesized using a supercritical carbon dioxide (scCO2) drying process. Polyimide hybrid aerogels of biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) containing surface-modified hollow mesoporous silica (AHMS) nanoparticles were prepared by chemical imidization and scCO2 drying. To avoid the high volume shrinkage of wet gels that occurs mainly during the drying process, AHMS nanoparticles were introduced to the network structure of the PI aerogels as a crosslinker. All aerogels exhibited a highly-interconnected, network-like structure of polyimide nanofibers with an average fiber diameter of approximately 27.6 nm and 92.8% porosity. These hybrid aerogels exhibited an excellent compression modulus, thermal stability, and high surface area, as well as low density, low shrinkage, and low thermal conductivity.