A novel moisture-controlled siloxane-modified hyperbranched waterborne polyurethane for durable superhydrophobic coatings

Superhydrophobic coatings have attracted extensive interest owing to their excellent water repellence property. However, low durability, environmentally harmful fabrication methods, and complex fabrication methods severely limit their widely practical applications. In this work, we demonstrate an eco-friendly, robust, superhydrophobic matrix coating based on siloxane-modified hyperbranched waterborne polyurethane (Si-HBPU) in combination with fluorinated silica nanoparticles (F-SiO₂). The superhydrophobic coating was constructed by convenient process of casting Si-HBPU onto the substrate, which was regulated by a moisture-controlled model, and then F-SiO₂ nanoparticles were uniformly seeded onto the surface of semi-cured Si-HBPU. The Si-HBPU covalently bonds to F-SiO₂ nanoparticles for the reason that Si-HBPU possesses many polar groups (such as Si-OH), which utilized the silanol groups to chemically bond with the surface hydroxyl of the substrate and F-SiO₂ nanoparticles to form a solid Si–O–Si cross-linking network. The resulted coating exhibited an excellent water repellency with contact angles of ∼ 163° and sliding angles of ∼ 3°. And benefiting from the establishment of the stable Si–O–Si binding, the modified coating demonstrates excellent mechanical robustness, and is capable of maintaining superhydrophobicity after 140 cycles of sandpaper abrasion. The resultant coating shows excellent anti-icing/deicing performance: the water-freezing time can be postponed to 2205 s at −20℃ and the ice adhesion is significantly lower than that of a pure copolymer coating (∼21.2 KPa). Moreover, the Si-HBPU/ F-SiO₂ coating also demonstrated excellence in scratch resistantance, anti-fouling and anti-corrosion performances. These remarkable performances may promote the development of large-scale operation and practical application.