Chitosan/silica hybrid aerogels with synergistic capability for superior hydrophobicity and mechanical robustness

Chitosan aerogels could be applied potentially in thermal insulation for energy-saving buildings, separation/ adsorption, and catalysis. However, disadvantages of chitosan aerogels include their hydrophilicity and low insufficient mechanical strength. Here we propose a silica-phase hybriding route to create chitosan/silica hybrid aerogels with a synergistic capability for favourable hydrophobicity and superior mechanical strength, demonstrating an emergent finding (hydrophobicity optimised with the improved mechanical strength). The aerogels exhibit low drying shrinkage (as low as 13.41 %), lightweight (lowest to 0.149 g cm-1), high-efficient thermal insulation (thermal conductivity as low as to 0.024 W m- 1 K-1 at room temperature and normal pressure) either under cryogenic (-196 degrees C) or high-temperature conditions, exceptional fire-retardancy (self-extinguishing in 1.8 s) and environmentally friendly characteristic (initial mineralisation after 10 d). High hydrophobic property (water contact angle up to 142 degrees) of the aerogels were achieved depending upon 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane of vapor deposition, presenting a discovery concerning substantial improvement of mechanical properties (up to 0.188 MPa at 5 % strain, increased by 25 %). Furthermore, we demonstrate that a plausible mechanism for simultaneous hydrophobic and mechanical enhancement is depending upon the modulation of networking skeletons at the nanoscale.

Automated summary

This study successfully prepared chitosan/silica hybrid aerogels with a silica-phase hybriding method, which exhibited favorable hydrophobicity and superior mechanical strength. The aerogels showed low drying shrinkage, lightweight, high-efficient thermal insulation, exceptional fire-retardancy, and environmentally friendly characteristic. The high hydrophobic property of the aerogels was achieved by vapor deposition of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane, which led to a substantial improvement in mechanical properties.