Synthesis of transparent and flexible superhydrophobic PDMS-EP/SiO2 coating with excellent mechanical and chemical durability

Superhydrophobic (SHP) coatings with transparency, flexibility, and self-cleaning properties are highly desirable for many applications. However, developing SHP coatings with excellent mechanical and chemical durability remains a challenge. In this work, the epoxy resin (EP) was modified with hydroxy-terminated polydimethylsiloxane (HO-PDMS) to improve its hydrophobicity and flexibility. Nano-silica (SiO₂) was added as reinforcing filler to prepare the PDMS-EP/SiO₂ coating. The coatings exhibited superhydrophobicity with a high water contact angle (WCA) of 155.5 ± 2.8° and a sliding angle (SA) less than 1° when the loading mass of nano-silica was 0.2 g. The coating maintained superhydrophobicity after 600 cm continuous rubbing by sandpaper, suggesting that the coating had remarkable mechanical durability. The coating also exhibited superior chemical stability because it retained strong hydrophobic property after immersing in strong acid and alkali solutions. Interestingly, the coating exhibited high transparency with an average transmittance of 80.7 % and outstanding flexibility as confirmed by bending-torsion tests. Moreover, the as-prepared coating also showed strong self-cleaning properties for effectively removing dust pollutants and excellent resistance to wetting from various liquids. It is believed that the facile and economical method offers an effective strategy and promising industrial applications for fabricating transparent, flexible and chemically stable superhydrophobic coatings.