Preparation of mechanically robust, self-healing superhydrophobic coatings based on novel fluorinated polyurethane via a “two-step” polycondensation process for applications in self-cleaning and anti-icing

Abstract

The demand for superhydrophobic coatings has been rapidly increasing, extending from applications in surface antifouling to surface anti-icing and self-cleaning, driving active exploration into mechanically robust superhydrophobic coatings. Fluorinated polyurethane (FPU) is considered a promising candidate for superhydrophobic coatings. However, most FPU-based superhydrophobic coatings exhibit limited adhesion to substrates and rely on nano-SiO₂ or nanoparticles to construct micro-nano hierarchical rough surfaces. However, it has been demonstrated that the rough surfaces created by nanoparticles reduce the effective contact area between the coating and the substrate, leading to accelerated wear of the coatings. Furthermore, to ensure the durability of superhydrophobic coatings, self-healing properties must also be considered. However, most self-healing superhydrophobic coatings developed so far require prolonged high-temperature conditions or external stimuli to restore their superhydrophobicity. Therefore, developing mechanically robust superhydrophobic coatings with self-healing capabilities remains a significant challenge. In this study, we synthesized a novel fully waterborne and self-healing FPU coating using a “two-step” polycondensation method. Even on the smoothest and hardest glass substrates, the coating retained its superhydrophobicity after 200 cycles of sandpaper abrasion, 200 cycles of tape peeling, a 6-hour water droplet test and acid-base resistance tests, outperforming most previously developed superhydrophobic coatings. Additionally, the coating exhibits excellent self-healing functionality. This allowed the coating to self-heal a 100 μm scratch and restore its superhydrophobicity within 56 min at room temperature without any external stimuli. The coating also exhibited excellent self-cleaning and delayed ice formation properties. This novel design and fabrication strategy provides a new perspective for surface protection.