Ultrarapid fabrication of robust and versatile superhydrophobic polysiloxane coatings with superior repellency

Superhydrophobic surfaces have tremendous application potential in various fields. One major decisive factor that determines superhydrophobicity is building micro/nanostructures on surfaces. However, the current fabrication of micro/nanotextured superhydrophobic coatings still suffers from complex procedures and poor mechanical strength of the structures. Polysiloxanes can be effectively synthesized through a rapid acid-catalyzed hydrolysis and polycondensation from alkoxy silanes. By combining a hard polysiloxane core and a low-surface-tension silane and appropriate nanoparticles, superhydrophobic coatings with high robustness should be produced easily and quickly using a polysiloxane system.

Viscous methyl polyhedral oligomeric silsesquioxane (methyl-POSS) resin was obtained by reacting methytriethoxysilane with water. Superhydrophobic polysiloxane coatings were prepared by using certain amounts of methyl-POSS, dimethyldimethoxysilane (DMDMS) and SiO₂ nanoparticles and a small amount of acid catalyst via different coating methods. The polysiloxane coatings were studied by atomic force and electron microscopies and by various chemical and mechanical durability tests.

The coating shows superior superhydrophobicity with water contact angles θ_A/θ_R over 170° and roll-off angle α < 1°, and can be obtained within seconds to minutes under ambient conditions. Especially, it presents high mechanical robustness against sandpaper abrasion for 8.0 m on a 2000-grit sandpaper under 2.5 kPa, knife-scratching, prolonged water drop impact. The structure demonstrates high chemical stability in multiple harsh environments, including heating, strong-acid, high-salt and boiling water conditions. The coating on fabric is demonstrated to be highly effective for oil-water separation, with an efficiency over 99.7 % and showing high durability over numerous cycles.