Sustainable marine antifouling coatings with temperature-triggered copper pyrithione release from chitosan-grafted microspheres

Current marine antifouling materials predominantly utilize external biocides. However, this method is characterized by uncontrolled burst release and short-term efficacy, necessitating frequent reapplication and causing significant environmental pollution. To address these issues, we developed a more sustainable approach by leveraging the controlled release capabilities of microsphere materials. Specifically, temperature-sensitive chitosan molecules were grafted onto microsphere shells using ionic cross-linking, and the resulting microspheres were incorporated into a polyurethane coating. Given the complexity of the marine environment, with varying seawater temperatures and biological activities across different sea areas, this strategy aims to enhance antifouling effectiveness and sustainability. The microspheres achieved an encapsulation efficiency of 97.33% for copper pyrithione. The chitosan functionalization enabled temperature-dependent release, with a critical transition threshold near 20 °C. Incorporation of these microspheres into polyurethane coatings not only augmented mechanical toughness but also synergistically improved antifouling performance and interfacial adhesion. Notably, the microspheres exhibited superior antimicrobial performance compared to direct copper pyrithione application. This research underscores the potential for developing environmentally friendly materials with temperature-controlled antifouling agent release and introduces a novel approach for long-lasting antifouling strategies.