Tailored TMES‐Modified Polyimide–Silica Aerogels for Enhanced Mechanical Performance and High‐Temperature Aerospace Applications

ABSTRACT The development of high‐performance thermal insulation and lightweight materials in aerospace applications requires overcoming the limitations of conventional aerogels. While polyimide (PI) aerogel offers flexibility and thermal stability, it suffers from shrinkage and a hydrophilic nature. In contrast, silica is an excellent insulator and fire‐resistant, but brittle and fragile in nature. These limitations highlight the challenges of sustaining mechanical resilience and thermal gradients in extreme aerospace applications. To overcome these limitations, we report a novel polyimide–silica (PSi) hybrid aerogel system fabricated via a dual‐step gelation and freeze‐drying process. The innovation in this study lies in the use of trimethylethoxysilane (TMES) as a co‐precursor, introduced for the first time in PSi systems, to chemically modify two silicas, TETMS (TEOS + TMES) and MTTMS (MTMS + TMES), and enhance their compatibility and surface hydrophobicity within the PI matrix. The PSi achieved low thermal conductivity (0.016 W m −1 K −1 ), low density (0.035 g cm −3 ), and low shrinkage (up to 2.86%), with high hydrophobicity (contact angle up to 139.5°), and excellent mechanical resilience, along with high thermal stability and fire resistance. These multifunctional characteristics demonstrate the potential of PSi aerogels for high‐performance applications in aerospace, where durability, flexibility and thermal properties are required.