Achieving rigid-flexible coupling in polyimide aerogels via biomimetic cross-scale architecture for extreme condition protection

Rapid advances in deep-space exploration and extreme protection technologies are driving demand for protective materials that combine thermal insulation with impact resistance. Nanofiber aerogels, owing to their low density and ultralow thermal conductivity, have emerged as promising candidates. However, their practical deployment remains limited by intrinsic mechanical fragility and the trade-off between thermal insulation and impact resistance. Inspired by the sturdy and flexible structural characteristics of bamboo, this work proposes a cross-scale interlocking and crosslinking architecture that integrates molecular crosslinking, nanofiber interlocking, and porous interlayer supporting networks. This design enables the polyimide composite aerogel (PAI) to deliver rigid–flexible protection under extreme conditions, exhibiting a tensile modulus of 4.17 MPa and a compressive modulus of 138 kPa, with less than 7% cumulative plastic deformation after 100 lateral compression cycles and a maximum stress retention of 99%. The PAI demonstrated excellent impact-buffering capability. When integrated into protective gear, it reduced impact-transmitted force by over 83% while maintaining high durability. Moreover, the PAI features ultralow density (0.045 g·cm^-3), minimal thermal conductivity (38 mW·m^-1·K^-1), and excellent flame retardancy (peak heat release rate = 9.36 kW·m^-2). Its synergistic balance of strength and flexibility with integrated thermo-mechanical protection offers a promising platform for next-generation protective systems.