Double‐Crosslinked Organic–Inorganic Hybrid Polyimide Aerogel Composites with Ultra‐Robust Toughness for Foldable Mechanical‐Thermal‐Coupled Protection

Abstract Aerogels excel in thermal insulation due to their porous structure, but their limited mechanical strength restricts broader applications. Thus, the development of aerogel composites for equipment/personnel against mechanical and thermal hazards in extreme environments necessitates more design paradigm. Herein, a novel double‐crosslinked polyimide aerogel composite (PIAC) with an organic–inorganic hybridization approach is prepared. This composite, incorporating amino‐modified SiO₂ nanoparticles to reduce shrinkage/density, offers exceptional thermal insulation from ‐110 °C to 300 °C, flame resistance, a low dielectric constant (1.4), a low thermal conductivity 0.0357 W (m K)⁻¹ and self‐cleaning properties. Meanwhile, the PIAC allows to be manipulated into various shapes and to withstand repeated folding and unfolding without damage. It boasts a tensile strength of 8.5 MPa (2.6‐fold enhancement) and a nominal elongation at break of 54% (17.5‐fold enhancement), representing the highest fracture toughness 32.99 × 10⁶ kJ m⁻³ (47.8‐fold enhancement) observed in aerogel materials to date. With the maximum energy absorption reaching 7.46 MJ m⁻³ when dissipating high‐impact forces, its substantial enhancement in energy absorption capacity is 60% over its predecessor, for the SiO₂ nanoparticles not only bolster the matrix strength but also amplify strain rate strengthening effect. The fabricated PIAC is poised for foldable mechanical‐thermal‐coupled protection where such attributes are highly coveted.