Effect of Linear versus Loop Topology on Antifouling Performance of Zwitterionic Brushes

High Resolution Image Download MS PowerPoint Slide Loop polymer brushes have recently attracted attention as a design concept for antifouling zwitterionic interfaces, but the conditions required for high antifouling performance and the molecular-level mechanisms underlying the antifouling behavior remain unclear. Here, linear and loop poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) brushes were compared under dynamic and low-shear conditions using ultrafiltration (UF) membranes and quartz crystal microbalance with dissipation monitoring (QCM-D), respectively. Under membrane pore flow, loop and linear brushes exhibited essentially identical fouling behavior when compared at matched effective brush states, indicating that topology effects are minor under high shear conditions. In contrast, under low-shear QCM-D conditions, loop brushes reduced protein adsorption relative to that of linear brushes. Step-resolved analysis showed that loop topology suppressed the initial rigid adsorption mode at lower molecular weight and the late-stage rigid adsorption mode at higher molecular weight. Molecular dynamics (MD) simulations indicated that loop brushes exhibit reduced chain fluctuation while maintaining a comparable average local hydration structure to that of linear brushes. Collectively, these results indicate that the antifouling advantage of the loop topology arises from constrained chain dynamics and is most pronounced under low-shear conditions.