Anti-bioadhesive polyurethane coatings enhanced by salicylic acid-carboxy-betaine modified nano-silica: Stepwise antifouling mechanism

Environmentally friendly antifouling coatings have received increasing attention in the field of marine infrastructures. In this work, a carboxy-betaine salicylate surface-modified silica nanofiller (QAs-SA@SiO 2 NPs) was synthesized and doped in polyurethane coatings (PU) to gain durable antifouling properties. The modified silica NPs were prepared by the covalent bond grafting method and then dispersed in PU paint to produce a kind of composite anti-fouling coating (QAs-SiO 2 PU). It is noted that the QAs-SiO 2 PU coating can adjust the release rate of salicylate according to environmental pH value. Once the salicylate layer was dissolved, the inner amphoteric carboxy-betaine molecules would be exposed to form a hydrated layer on QAs-SA@SiO 2 NPs, thus realizing a step-by-step antifouling performance. The experimental results show that the 7 wt% addition of QAs-SA@SiO 2 filler in the PU coating can reduce protein adhesion by 99.1 %, bacterial adhesion by 99.8 %, and chlorella adhesion by 95.0 %, presenting a significant mussels-repellence ability compared to the pristine PU coating. This work may provide a promising approach to designing eco-friendly and durable marine anti-fouling and anti-corrosion coatings.