Novel indole-based self-polishing environmentally friendly acrylic antifouling coatings

Marine biological pollution poses a significant threat to both marine activities and human biomedical applications. The pivotal solution lies in the development of environmentally friendly antifouling coatings. In this study, indole derivatives containing carbon-carbon double bond (specifically allyl 5-Cl/NO2-indole-carboxylate, abbreviated as ACIC/ANIC) were synthesized from 5-Cl/NO2-indole and incorporated into zinc acrylate resins via N-acylation reaction. The resulting mixture of zinc acrylate resin and polycaprolactone (PCL) was integrated into acrylic urethane lacquers (AUL), and the self-polishing and antifouling properties of these lacquers were comprehensively evaluated through antimicrobial experiments, algal inhibition studies, static simulations, and antifouling experiments conducted in marine environments. The findings demonstrate that these coatings not only exhibit effective self-polishing properties but also outperform pure zinc acrylate resins in terms of antifouling properties. Moreover, the incorporation of PCL prolongs the service life of the coatings. In specific, the coatings containing ANIC showcased impressive antimicrobial activity with antimicrobial rates of 92.79 % and 99.71 % against typical Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria, respectively. Additionally, the algal inhibition rate against Nitzschia closterium and Phaeodactylum tricornutum reached 90.35 % and 79.74 %, respectively. In summary, ANIC emerges as an efficient and environmentally friendly coating material, offering a promising approach to address the economic and operational problems associated with marine bio-pollution.