Double‐Phase‐Networking Polyimide Hybrid Aerogel with Exceptional Dimensional Stability for Superior Thermal Protection System

Abstract Polyimide aerogels have been extensively used in thermal protection domain because they possess a combination of intrinsic characteristics of aerogels and unique features of polyimide. However, polyimide aerogels still suffer significant thermally induced shrinkage at temperatures above 200 °C, restricting their application at high temperature. Here, a novel “double‐phase‐networking” strategy is proposed for fabricating a lightweight and mechanically robust polyimide hybrid aerogel by forming silica–zirconia‐phase networking skeletons, which possess exceptional dimensional stability in high‐temperature environments and superior thermal insulation. The rational mechanism responsible for the formation of double‐phase‐networking aerogel is further explained, generally attributing to chemical crosslinking reactions and supramolecular hydrogen bond interactions derived from the main chains of polyimide and silane/zirconia precursor/sol. The as‐prepared aerogels exhibit excellent high‐temperature (270 °C) dimensional stability (5.09% ± 0.16%), anti‐thermal‐shock properties, and low thermal conductivity. Moreover, the hydrophobic treatment provides aerogels high water resistance with water contact angle of 136.9°, further suggestive of low moisture content of 3.6% after exposure to 70 °C and 85% relative humidity for 64 h. The proposed solution for significantly enhancing high‐temperature dimensional stability and thermal insulation provides a great supporting foundation for fabricating high‐performance organic aerogels as thermal protection materials in aerospace.