Surface charge-driven WPU/hPDMS antibiofouling coatings

Marine biofouling associated with marine infrastructures can considerably reduce structural performance, durability and operational efficiency, underscoring the need for non-biocidal and eco-friendly antibiofouling coatings. Water-based polyurethane (WPU) has emerged as an eco-friendly alternative to solvent-borne coating matrices in recent years. However, the limited surface chemistry of WPU restricts its versatility and effectiveness as a long-lasting binder in marine applications. Herein, WPU has been chemically functionalised by hydroxy-terminated polydimethylsiloxane (hPDMS) to enhance its surface chemistry, specifically surface charge, in controlling marine biofouling. The hPDMS functionalised WPU demonstrated improved surface charge properties with the zeta potential ranging between − 88.38 ± 0.90 mV, while retaining hydrophilic wettability. This hydrophilicity, combined with the highly negative surface charge of WPU/hPDMS-6 is desirable for augmented antibacterial properties, acting mainly through short-range interactions under marine salinity which was studied against Gram-negative ( Escherichia (E.) coli ) and Gram-positive ( Staphylococcus (S.) aureus ) incubated under constant shaking to simulate marine-like conditions. Despite the lack of any integrated biocidal or antibacterial agent, the WPU/hPDMS-6 coating showed bacterial reductions of ~ 25.31% for E. coli and ~ 29.03% for S. aureus , while Control-WPU alone showed ~ 4.71% and ~ 4.15%, respectively. The protein adsorption assays revealed that relative to the bare substrate, BSA adsorption was reduced by ~ 23.94% for Control-WPU and ~ 20.37% for WPU/hPDMS-6, whereas lactoferrin adsorption decreased by 31.56% and 23.31%, respectively. Thus, these results provide new insights into the development of charge-driven, biologically less active polymeric binders to reduce the reliance on high loading of toxic biocides for mitigating marine biofouling.