Preparation of Superhydrophobic Porous SiO₂ Aerogel Using Methyl Trimethoxy Silane Single Precursor and Superhydrophobic Cotton Fabric Coating from It.

Superhydrophobic cotton fabrics were prepared by simultaneous incorporation of SiO₂ aerogel particles and polydimethylsiloxane (PDMS). The SiO₂ aerogels were synthesized via acid-base catalyzed sol-gel reaction with methyl trimethoxy silane (MTMS) as the single precursor and oxalic acid and ammonium hydroxide as the catalyst in methanol (MeOH) solution by drying under ambient pressure. The preparation parameters (e.g., MTMS/MeOH molar ratio, oxalic acid/MTMS molar ratio, gelation pH value, and gelation temperature) had great influences on the density and porosity of the SiO₂ aerogel. The obtained SiO₂ aerogel had low density, high porosity and high specific surface area, showing the typical rough mesoporous structure. The prepared bulk SiO₂ aerogel displayed excellent superhydrophobicity with a water contact angle (WCA) of 151.0 ± 0.8°. Superhydrophobic cotton fabric with a WCA of 155.6 ± 0.9° for a 5 L water droplet was successfully obtained by simply coating the PDMS/SiO₂ aerogel composite solution via dip-pad-cure process. This could be attributed to the combination of SiO₂ aerogel particles with porous rough microstructure, high specific surface area and PDMS adhesive layer with low surface energy. The effect of PDMS/SiO₂ aerogel coating treatment on the mechanical strength properties of the cotton fabrics was negligible. This simple approach may pave the potential way for practical applications.