Binary-Network structured PI@SiO 2 nanofibrous composite aerogels with temperature invariant superelasticity for thermal insulation

The extreme temperatures encountered in aerospace pose formidable challenges to the performance of elastic materials in spacecraft and related apparatus. Traditional organic insulation materials face hindrance due to inadequate fire resistance, while inorganic insulation materials are often brittle. Herein, we designed binarynetwork composite aerogels with dual-crosslinked PI nanofibers as the scaffold and uniformly distributed silica nanoparticles within the anisotropic aerogel matrix. Owing to the dual-crosslinked PI nanofiber network, the resulting PI@SiO 2 aerogel can withstand 1000 cycles of radial fatigue testing under 50 % compressive or buckling strains, maintaining structural stability across a wide angular frequency range of 0.1 -100 rad/s. DMA testing shows that PI@SiO 2 aerogel can endure 100,000 fatigue cycles from 25 to 300 degrees C, with storage modulus and loss modulus, and damping ratio, indicating robust long-term performance over a wide temperature spectrum. Even with liquid nitrogen (-196 degrees C) and butane torch flames (1100 degrees C), PI@SiO 2 aerogel preserves its superelasticity through repeated compressions. Moreover, the composite aerogel exhibits excellent thermal insulation, with low thermal conductivity (27.2 mW m -1 K -1 ), and reachs the top flame-retardant level (UL94V0). This work not only establishes a novel pathway for constructing polymer-based materials with temperatureinvariant superelasticity but also holds great promise for extensive applications in ongoing and near-future aerospace exploration.