Self-healing polydimethylsiloxane antifouling coatings based on zwitterionic polyethylenimine-functionalized gallium nanodroplets

There is an urgent need to develop effective and eco-friendly nanostructured coatings for marine antifouling to replace traditional coatings, while ensuring they do not lead to environmental hazards. Gallium-based liquid metal (GLM), which has unique antibacterial and non-toxic properties, has potential for applications in antifouling. In this study, GLM nanodroplets modified with zwitterionic polymer (polyethylenimine-quaternized derivative, PEIS) based antifouling agent were prepared successfully via sonication and Michael-addition, which could potentially be incorporated into the polydimethylsiloxane coating (PDMS) as a functional filler. A series of characterization methods, such as infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, have proved the successful modification of GLM nanodroplets with PEIS. The PEIS functionalized GLM nanodroplets exhibit good anti-bacterial properties due to synergistic bactericidal activity of Ga³⁺ stemming from GLM nanodroplets and the quaternary ammonium group from zwitterionic polymer PEIS. The synergistic anti-bacterial properties of PEIS-GLM nanodroplets and strong surface hydration of zwitterionic polymer PEIS result in remarkable antifouling performance of the filler. Subsequently, through the observation of the cross section, the as-prepared PEIS modified GLM nanodroplets exhibit good dispersibility in the PDMS coating, which also ensures that the PEIS-GLM@PDMS coating has satisfactory antifouling effect (removal of above 90% bacteria and 70% microalgae). Furthermore, the PEIS modified GLM nanodroplets endow the PDMS coating with self-healing properties by reason of the crosslinking of unreacted vinyl in PDMS by exposed GLM initiating polymerization under external mechanical force.