Anion-Influenced\nHydration and Layering Vastly Modulate\nPolyzwitterionic Brush Responses

This study investigates the influence of different anions\non the\nhydration states and conformational changes of poly(sulfobetaine methacrylate)\n(PSBMA) brushes, unraveling their intricate role in modulating tribomechanical\nproperties and antifouling performance. Through bimodal atomic force\nmicroscopy (AFM), we reveal that anion identity affects the layered\nstructure thicknesses of PSBMA brushes in accordance with the Hofmeister\nseries. Enhanced screening of dipole–dipole interactions and\nincreased hydration were observed with higher concentrations of more\nchaotropic counterions, showcasing the anti-polyelectrolyte effect\n(APE), a phenomenon that was not observed in highly kosmotropic sulfate\nanions. Infrared spectroscopy highlighted the impact of anions on\nthe incorporation of strongly H-bonded water clusters within the PSBMA\nchains. Our findings underscore the complex interplay of interfacial\ninteractions (chain dipole–dipole, ion-chain dipole, ion–water,\nand water-chain dipole), leading to variations in tribomechanical\nbehavior and antifouling performance of PSBMA brushes. Pearson correlational\nanalysis with anion descriptors further elucidated these relationships,\noffering insights for tailored material design in engineering applications,\nthus advancing materials science and biotechnology.