Synergistic antifouling behaviors between zwitterions and ZnO nanoparticles in moisture-curable polyacrylate coatings

The current zwitterionic antifouling (AF) coatings generally have limited broad-spectrum AF ability, poor compatibility with coating matrixes and weak mechanical properties due to high water adsorption. In this work, we tried to incorporate zwitterionic component, namely, (N-methoxyacylethyl)-3-aminopropyltriethoxysilane (MAPS) and ZnO nanoparticles into a moisture-curable polyacrylate (MCP) to fabricate marine AF coatings. AF behaviors were examined by laboratory and field assays towards different target foulants. Laboratory anti-protein ability towards bovine serum albumin promoted with the increase of MAPS and/or ZnO contents, verifying their synergistic AF effect towards the earliest pollutant in biofouling process. Laboratory AF test towards bacterium Pseudoalteromonas marina and diatom Cylindrotheca closterium also exhibited the synergistic AF effect between zwitterions and ZnO nanoparticles, however, depending on their concentrations. Under the highest contents of MAPS (i.e., 30 %) and ZnO nanoparticles (i.e., 50 %), the coatings showed the best laboratory AF properties, with the antibacterial rate, sterilization rate and anti-diatom rate of 86.7 %, 71.8 % and 87.6 %, respectively. As for the marine field AF performance, the ZnO nanoparticles content had a significant effect on improving the field antibacterial ability, while the effect of MAPS was not obvious. But for the field anti-diatom assay, MAPS and ZnO nanoparticles depicted synergistic effect on diatom resistance. After field exposure for 52 d, the coatings with 30 % MAPS and 50 % ZnO nanoparticles revealed the best comprehensive AF performance, i.e., 82.4 %, 95.0 % and 95.5 % reductions towards bacteria, diatoms and mussels, respectively, and moreover, maintained pencil hardness of 2 H after immersed in ASW for 9 months. Besides, the coatings were capable of restoring their original oleophobicity and AF capability after mechanical abrasion.