Molecular dynamics study of protein adsorption on zwitterionic and imidazolium salt modified antifouling polyurethane...

The undesired adhesion and accumulation of marine organisms on vessel hulls pose significant challenges to maritime operations. Following the prohibition of organotin-based agents, there is an increasing demand for environmentally sustainable antifouling materials. In recent years, polymeric coatings incorporating zwitterionic moieties or imidazolium-based functionalities have emerged as promising candidates owing to their outstanding resistance to biofouling. However, the molecular-level interactions and antifouling mechanisms governing these systems remain insufficiently understood. In this work, molecular dynamics (MD) simulations are employed to systematically elucidate the underlying antifouling mechanisms of three representative membranes: pristine polyurethane (PUR), polyurethane functionalized with zwitterionic groups (PUZ), and polyurethane modified with both zwitterionic and imidazolium moieties (PUB). An extensive analysis of protein conformational perturbation, adsorption behavior, interfacial hydration capacity, and surface electrostatic characteristics is conducted to reveal the molecular-level mechanisms governing antifouling performance. PUZ establishes a dense hydrogen bond (HBond) hydration layer, whereas PUB displays a more spatially organized and localized interfacial water structure, which, together with strong electrostatic repulsion and a heterogeneous surface potential, effectively suppresses protein adsorption and multi-point anchoring. As a result, PUB shows the weakest protein adsorption (-52.95 kJ mol^-1) and the best antifouling performance. These findings provide molecular insights into hydration-mediated antifouling mechanisms and highlight the critical role of MD simulations in uncovering structure-property relationships, and guide the rational design of sustainable polymeric antifouling materials.