High-adhesive superhydrophobic litchi-like coatings fabricated by in-situ growth of nano-silica on polyethersulfone surface

This work presents the preparation of durable superhydrophobic polyethersulfone (PES) composite coating with large water contact angle of 157.2 ± 1.3° and small sliding angle of 3 ± 0.5°. The interface bonding force between PES and SiO2 nanoparticles was enhanced through the dopamine self-polymerization on the surfaces of PES particles during the sol-gel process. After surface modification with 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS), superhydrophobic PES-PDA-SiO2-POTS coating was easily prepared by a simple one-step spraying method with less than 2.6 wt% SiO2. The dosage of nanoparticles to establish micro/nano structures for superhydrophobic coating was much less than the previously reported, which is beneficial to improve the interface bonding force between PES and SiO2. The prepared coating can still remain superhydrophobicity even after 84 h of immersion in a 3.5 wt% NaCl solution. The durable superhydrophobicity was mainly attributed to the litchi-like structure that trapped more air to effectively prevent water infiltration. Combined with the high interface bonding force of PES-SiO2 and the low concentration of SiO2, the adhesive ability of the coatings accorded with Grade 0 of GB/T9286, which represented the best adhesive strength. In addition, the wear life of the PES-PDA-SiO2-POTS coating was prolonged to 8 times than that of PES/SiO2/POTS coating. Potentiodynamic polarization plots indicated that the coating had great corrosion resistance, low corrosion current density of 9 × 10−9 A/cm2 and high corrosion protection effect of 99.99%. The superhydrophobic PES-PDA-SiO2-POTS coating can be also highly applied on different substrates. It is believed the PES-PDA-SiO2-POTS coating may have great potential for large-scale applications.