Mechanically robust, self-healing superhydrophobic anti-icing coatings based on a novel fluorinated polyurethane synthesized by a two-step thiol click reaction

Superhydrophobic coatings have big potential to be used in anti-fouling, drug reduction, anti-icing applications. The fabrication of a robust superhydrophobic coating on hard and smooth substrates still remains challenging. It was reported that fluorinated polyurethane (FPU) was a good candidate for superhydrophobic coatings. However, since the preparation methods of FPU at present are rigid and limited, and the substrate adhesion of FPU is unsatisfied, robust FPU-based superhydrophobic coatings on hard and smooth substrates were rarely reported. In this work, a mechanically robust SiO₂-FPU superhydrophobic coating on various substrates was synthesized by a two-step thiol click reaction. The branched fluoroalkyl chains were grafted to the polyurethane backbone and then the flexible fluoroalkyl chains tended to migrate to the surface during solvent casting while the strong urethane linkages located at the substrate. The most promising SiO₂-FPU coating on glass substrates could maintain superhydrophobic after 30 m sandpaper abrasion, 450 tape peeling cycles and 1.5 h water dripping (~14400 water drops), which are better than the coatings in most of published works. Significantly, the SiO₂-FPU coating could recover the superhydrophobicity rapidly after damages because of the accelerated migration of flexible and branched fluoroalkyl chains to the coating surface and the rebuilding of nanoscale structure under heating. The static and the dynamic anti-icing characterizations indicated that the SiO₂-FPU coating showed great icing-delaying performance. Both the novel preparation strategy and the FPU-based coating would provide a new perspective in surface protection.