Ultralight and Flexible Subnanowire Aerogels for Intrinsically Hydrophobic Thermal Insulation

Aerogels are regarded as the next generation of thermal insulators; however, conventional aerogels suffer from issues such as brittleness, low moisture resistance, and a complex production process. Subnanowires (SNWs) are emerging materials known for their exceptional flexibility, toughness, intrinsic hydrophobicity, and gelling capabilities, making them ideal building blocks for flexible, tough, hydrophobic, and thermally insulating aerogels. Herein, we present a simple and scalable strategy to construct SNW aerogels by freeze-drying hydroxyapatite (HAP) SNW dispersions in cyclohexane. The resulting aerogels consist of three-dimensional porous flakes composed of thin layers of SNW bundles. They exhibit numerous outstanding properties, including ultralow density (12.33 mg·cm^-3), high porosity (99.15%), remarkable flexibility and toughness, and excellent thermal insulation properties (27.53 mW·m^-1·K^-1). Because the HAP SNWs consist of hydroxyapatite cores capped with hydrocarbon chains, the aerogels demonstrate intrinsic hydrophobicity (138° water contact angle) and superior thermal stability compared to polymer foams. Furthermore, the HAP SNW aerogels can effectively shield against infrared radiation due to their low thermal conductivity. This work suggests that SNWs can serve as superior building blocks for flexible, tough, and intrinsically hydrophobic aerogels, paving the way for future applications in thermal insulation.