Ultralight, low-shrinkage copolyimide aerogels with excellent mechanical strength for flexible thermal protection

Polyimide aerogels (PIAs) have garnered considerable attention for thermal protection owing to their outstanding high-temperature resistance, wide operational-temperature range, and flexibility. However, their flexibility improvement, drying-shrinkage reduction, and thermal-insulation and mechanical-property enhancements still remain research hotspots. Herein, flexible copolymer PIAs were synthesized via copolymerization modification–chemical imidization, which exhibited outstanding mechanical properties, ultralow dry shrinkage, and highly efficient thermal insulation. By taking full advantage of the comonomer 3,3′,4,4′-biphenyltetracarboxylic dianhydride has a rotatable single bond and increases a high free volume of the involved chain, the PIAs achieves a notable transition from brittleness to high flexibility. Results demonstrate that the 5 %-weight-loss temperature of the PIAs is up to 512.6 °C in air and that their thermal conductivity is as low as 15.1 mW·m⁻¹ K⁻¹. Concurrently, the interactions among the involved nanochain segments contribute to the formation of a three-dimensional network structure with high nodal connectivity and robust crosslinking, enhancing the PIA mechanical strength, with the tensile strength and modulus being 17.633 and 468.41 MPa, respectively. Further, the synthesized PIAs exhibit a low density of 0.079 g/cm³ and low drying shrinkage of 4.323 %. Overall, this research introduces a novel method for developing flexible, low-shrinkage polymer materials with excellent thermal insulation and mechanical properties, exhibiting vast potential for application in aerospace exploration efforts.