Exploring the Antifouling Mechanism of Zwitterionic Monomer-Grafted PDMS Membranes at the Atomic Level: A Molecular Dynamics Simulation Study

Marine biofouling is a significant challenge faced by the entire shipping industry, as it can lead to increased hull roughness, which in turn increases navigation resistance and power consumption as well as more severe accelerated corrosion. Zwitterionic polymers show great promise in the design and fabrication of marine antifouling coatings due to their environmentally benign antifouling characteristics. However, it remains challenging to experimentally monitor the molecular-level variations in mobility and surface structural characteristics of zwitterionic membranes in water, which significantly hinders the rational design and optimization of antifouling coatings. In this work, molecular dynamics (MD) simulations are systematically employed to investigate the hydration behavior of modified polydimethylsiloxane (PDMS) with varying zwitterionic grafting densities and their interactions with biological fouling. The influence of surface functional groups in zwitterionic polymers on hydration layer formation is elucidated at the molecular level, and the effect of zwitterionic grafting density on biofouling-related interfacial properties is revealed. The results show that higher zwitterionic grafting densities lead to formation of more compact hydration layers around the modified membranes, which not only enhance hydrogen bond network stability but also significantly reduce the water diffusion rate along membrane surfaces. Further examination of dynamic fouling processes (using mussel adhesive proteins as representative foulants) in saline solutions demonstrates that membranes with higher grafting densities effectively increase the energy barrier for protein adsorption and weaken protein–membrane interactions. Structural analysis reveals that significant conformational changes occur on high grafting density membrane surfaces when protein secondary structures remain intact during simulations. These simulation results are consistent with actual marine field test data, confirming their reliability. This work provides important theoretical foundations for the development of high-performance antifouling materials.