Waterborne Polyurethane/Cellulose‐Reinforced Silica‐Based Aerogels for Efficient Thermal Insulation and Piezoresistive Sensing

ABSTRACT Aerogels, as archetypal ultralight porous materials, exhibit great potential in thermal insulation and functional materials owing to their extremely low thermal conductivity and high specific surface area. However, conventional silica aerogels (SA) suffer from structural brittleness due to the rigid inorganic skeleton, limiting their use in flexible or deformation‐prone environments. To address this issue, we propose a cooperative enhancement strategy using cellulose nanofibers (CNF) and waterborne polyurethane (WPU) to construct a composite silica aerogel. This approach forms a “rigid–flexible complementary” three‐dimensional network, where CNF provides flexible support and WPU enhances interfacial adhesion and energy dissipation. Compared with conventional polymer‐reinforced aerogels, this strategy improves organic–inorganic interfacial interactions at the nanoscale, leading to enhanced mechanical robustness and stress transfer efficiency. The resulting composite aerogel achieves a low thermal conductivity of 0.02555 W·m −1 ·K −1 , a high compressive strength of 221.7 kPa, stable fatigue resistance over 200 cycles, and a fast strain response time of 43 ms. This study offers a novel design paradigm for high‐toughness thermal insulation aerogels and lays a material foundation for their practical applications in flexible insulation and high‐temperature sensing fields.