Transparent hybrid coatings for marine antifouling: Synergizing amphiphilicity, nanocellulose lubrication, and electrostatic repulsion

The development of environmentally compliant marine antifouling coatings requires innovative strategies that transcend conventional biocide-dependent approaches. We present a transparent silicone-based hybrid coating integrating amphiphilic telomers, castor oil-modified cellulose nanocrystals (CO-CNs), and cholic acid through covalent bonding, demonstrating high transparency (>90 % transmittance) and excellent flexibility, which also demonstrates strong adhesion (~3.93 MPa) to the substrate, ensuring its use in harsh marine environments. This system achieves exceptional antifouling performance through synergistic interplay of three fundamental mechanisms: a microscale amphiphilic surface, nanocrystal-enabled lubrication (friction coefficient reduction from 0.52 to 0.08), and enhanced electrostatic repulsion (zeta potential of −110.22 mV at pH 8). The microscale hydrophobic/hydrophilic heterogeneities from amphiphilic telomers disorient microorganisms. Notably, incorporating CO-CNs creates abundant lubrication sites on the coating surface that reduce microorganism contact area. Simultaneously, cholic acid-derived carboxyl groups amplify electrostatic repulsion synergistically against negatively charged microorganisms, as verified by 98 % reduction in bacterial adhesion forces (0.29 nN vs 7.29 nN for commercial PDMS) as evidenced by fluidic force microscopy. Laboratory evaluations demonstrated 95 % inhibition of protein adsorption and 99 % reduction in diatom settlement compared to those of commercial PDMS. Furthermore, field trials in Qingdao seawater revealed sustained antifouling efficacy over 180 days, with coated surfaces maintaining >90 % macrofouling resistance through seasonal variations. The demonstrated synergy between amphiphilicity, surface lubrication, and electrostatic repulsion offers significant potential for sustainable maritime applications.