Highly Effective Functionalized Coatings with Antibacterial and Antifouling Properties

One of the current challenges in maritime antifouling is the development of new nanostructured coatings which can replace the old protection coatings based on tributyltin biocides prohibited by EU and US legislation as ecologically dangerous. In our study, antibacterial/antifouling polymer coatings containing innovative dual functionalized nanocapsules demonstrate high antifouling activity in various tests. Capsules are MCM-48 SiO₂ nanoparticles loaded with eco-friendly 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) antifouling agent and decorated with dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride or dimethyltetradecyl [3-(triethoxysilyl) propyl] ammonium chloride (quaternary ammonium salts, QASs) also possessing antifouling activity. Cross section images of the coatings demonstrated the absence of the capsule aggregates in the coatings with slight increase of the surface roughness. The formulated coatings revealed excellent antibacterial performance against E. coli and Staphylococcus aureus according to ISO 22196:2011 protocol. This antifouling activity was also confirmed by immersion of the coated polyvinyl chloride (PVC) panels at a depth of 8–9 m in the sea (Eilat, Israel). Biofouling coverage of 6.9% was observed for nanocapsules-loaded coatings (5 wt % concentration of nanocapsules) compared to the 49% of the coverage for nonmodified coating after 6 months of immersion. The nanocapsules-loaded coatings with dual antifouling functionality demonstrated antifouling activity even after complete release of encapsulated DCOIT because of chemically attached QAS groups on the nanoparticles surface. Moreover, active antifouling materials presented in nanocapsules do not demonstrate any toxicity to the brine shrimps Artemia salina, which are widely used in the food industry.