pH-Responsive Controlled Release of Antifouling Agents from Polysiloxane Coatings for Marine Propellers

Traditional antifouling coatings often lack the combined capabilities of static antifouling and dynamic fouling-release, which are critical for marine propellers. This study addresses this limitation by developing pH-sensitive polysiloxane coatings that integrate both functionalities. Two coating systems, PS-Levo and PS-PLL, were synthesized by incorporating levofloxacin (Levo) and polylysine (PLL) as antifouling agents, respectively. PS-Levo was synthesized via an epoxy-carboxylic acid ring-opening reaction, while PS-PLL was obtained through an amine-hydrosilylation reaction, using APTES as the curing agent. A key innovation of these coatings is their pH-triggered hydrolysis. Marine microorganisms that form biofilms on the coating surface can alter the microenvironmental pH through their metabolic activities, either lowering or raising it, thereby promoting the release of antifouling agents. The coatings exhibited remarkable antifouling efficacy, achieving bactericidal and anti-algal rates of over 99% and 97%, respectively. Following a 180-day immersion of the coated panels in natural seawater, minimal marine biofouling adhered to the coated surfaces and could be effortlessly removed by simple rinsing, thereby demonstrating excellent static antifouling and dynamic fouling-release performance. Moreover, the PS-Levo and PS-PLL coatings exhibited outstanding adhesion, mechanical properties, and corrosion resistance. This research introduces an innovative strategy for combating biofouling on marine propellers and presents significant potential for practical applications in the marine antifouling industry.