Eco-friendly quaternary ammonium modified PDMS coatings with integrated anti-bacterial, anti-algae, and marine anti-fouling properties

As the ecological risks associated with the use of copper and booster biocides in anti-fouling coatings become increasingly apparent, the design and development of environmentally friendly marine anti-fouling coatings present novel challenges. In this study, we developed a polyurethane (PU) modified polydimethylsiloxane (PDMS) copolymer (PDMS-PU) and then quaternized the copolymer using four brominated alkanes with varying carbon chain lengths. The soft segment PDMS, hard segments N-methyldiethanolamine (MDEA) and isophorone diisocyanate (IPDI), and strong cross-linked hydrogen bonds ensure the PDMS-PU polymer coatings with enhanced mechanical properties, good durability and static anti-algae properties. The quaternization of the coating resulted in a significant enhancement in its anti-bacterial and anti-algae performance. The modified coatings exhibited 99.1 % anti-bacterial inhibition against Staphylococcus aureus and Escherichia coli, and achieved 88.9 % and 80.2 % anti-algae inhibition rate for Chlorella and P. tricornutum, respectively. The anti-algae mechanism involves an increase in membrane potential followed by rupture, resulting in cellular damage and DNA leakage. In addition, the PDMS-PU-X coatings (where X = 4, 8, 12, 16, representing the number of carbon atoms in the bromoalkanes used for quaternization) demonstrated excellent anti-fouling performance against marine microorganisms, liquid pollutants, and pseudo-barnacle adhesion. The laboratory zebrafish toxicity tests further confirmed the coatings' non-toxicity toward non-target organisms. This study provides a novel strategy for developing environmentally friendly marine anti-fouling coatings.