Superhydrophobic coatings with improved mechanical robustness based on polymer brushes

•Extremely water repellant surfaces are fabricated by one-step spray-coating.•Enhanced mechanical robustness is provided by using polymer brushes as the matrix.•Transparent and superhydrophobic coatings are demonstrated.

Superhydrophobic surfaces show great promise for applications that range from self-cleaning windows to anti-icing air-crafts. Practical applications require development of methods and materials for one-step fabrication of such coatings with sufficient mechanical robustness on large surface areas at low costs. Spray-coating of nanoparticles functionalized with low energy molecules can meet all these requirements except the challenges associated with the mechanical robustness of the coatings. Here, we demonstrate that the mechanical robustness of the spray-coated films can be improved by engineering the polymer matrix. Hydroxyl-terminated polystyrene (PS-OH) serves as a matrix for dispersing silica nanoparticles (12 nm) functionalized with fluorinated silanes. Hydroxyl ends of the PS-OH facilitate chemical and physical interactions with the underlying substrate, through grafting of polymer chains to form brushes and by presenting hydrophilic groups, respectively. The fabricated films showed a high level of surface roughness with water contact angles (θ) greater than 170°. The coatings retained their superhydrophobic behavior (θ > 150° and sliding angle < 10°) upon abrasion with sand grains at impact velocities that are lower than ~ 10 km/h. The presented approach allowed for fabrication of transparent superhydrophobic coatings which transmit ~ 85% of the visible light that passes through a bare glass slide.

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