Synthesis and characterization of rigid and thermostable polyimide aerogel crosslinked with tri(3-aminophenyl)phosphine oxide

Polyimide (PI) aerogels cross-linked with a three amino compound tri(3-aminophenyl)phosphine oxide (TAPO) were synthesised by 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (4,4′-ODA) through chemical imidization method. Supercritical CO2 was used for drying the PI gels to fabricate nanoporous aerogels with tunable densities ranging from 0.09 to 0.32 g/cm3, and the specific surface areas between 198 and 340 m2/g. To enhance the thermal stability of the BPDA-ODA-based PI aerogels, PMDA was introduced into the formulating oligomer chain. The results showed that with the increase of PMDA concentration, the 5 wt% thermal degradation temperature of PI aerogels could rise to around 600 °C and the glass transition temperature could increase from 269 to 306 °C, which makes them ideal insulation materials for aerospace and other applications.