Fabrication of a pH-responsive carrier for antifoulant delivery and investigation of its controlled release properties

A pH-responsive nanocomposite enables on-demand antifoulant release. • Sharp release triggered by biofilm acidification minimizes environmental leakage. • The smart coating retains PDMS properties with enhanced pH-switchable antifouling. In this work, a pH-responsive antifouling system was developed to address the problem of inefficient use of antifoulants in antifouling coatings. A nanocomposite (MSN-MOF-CA@BIT) was fabricated via a layer-by-layer (LBL) assembly strategy, integrating mesoporous silica with a metal-organic framework for controlled antifoulant (BIT) release. This composite was then incorporated into a polydimethylsiloxane (PDMS) coating matrix. The composite powder exhibited clear pH-dependent release kinetics, with minimal release at seawater pH and accelerated release under acidic conditions. Correspondingly, it demonstrated potent, pH-enhanced antibacterial activity, achieving rapid bacterial eradication in acidic environments. Within the PDMS coating, the composite showed excellent dispersibility, as confirmed by laser confocal microscopy. The coating’s surface roughness increased moderately with filler loading, while its low surface free energy was preserved (<20 mJ/m²). Mechanically, the composite acted as a reinforcing filler, increasing the fracture elongation to 345.6% and the tensile strength to 0.628 MPa at a 10 wt.% loading. Most importantly, the composite coating retained its pH-responsive functionality. Immersion tests confirmed the stability of the encapsulated BIT during coating preparation and its on-demand release in service. Bacterial adhesion assays directly verified the coating's pH-responsive antifouling efficacy: significantly less biofilm formed under acidic conditions triggered by bacterial metabolism, demonstrating the system's ability to prevent fouling expansion proactively. In summary, this study successfully fabricates and validates a novel nanocomposite-based pH-responsive controlled-release coating. It achieves efficient, environmentally triggered antifoulant utilization while maintaining and even enhancing the key physical properties of the PDMS coating, showing great promise for sustainable antifouling technologies. Download: Download high-res image (352KB) Download: Download full-size image