Synergizing Tunable Hydration and Robust Adsorption in Cobaltocenium‐Based Metallo‐Polyzwitterions for Superior Water Lubrication

ABSTRACT

Polyzwitterions are promising candidate for aqueous lubrication due to their strong hydration capability, yet conventional polybetaines suffer from an intrinsic trade‐off between hydration and surface adsorption. Herein, we developed a series of metallo‐polyzwitterions (denoted as PZ‐R) using cobaltocenium as the cation and sulfonate as the anion via thiol‐ene click polymerization and stepwise post‐polymerization modification. The zwitterionic side groups exhibit strong hydration behavior due to their high water‐binding capacity, while the thioether linkages and cobaltocenium moieties synergistically promote efficient adsorption on metal surfaces through coordination and electrostatic interactions. This synergy overcomes the intrinsic trade‐off of conventional polyzwitterions, facilitating the spontaneous formation of a robust lubrication film. Tribological evaluations revealed that PZ‐R polymers serve as effective aqueous lubrication additives, delivering significant friction reduction and wear resistance under various test conditions. Among the series, PZ‐C ₈ achieved superior performance, reducing the coefficient of friction by 81% (to 0.123), the wear depth by 44% (to −1.781 µm), and the plastic pile‐up by 73% (to 0.671 µm) relative to pure water, with robust performance maintained across varying loads, frequencies, and prolonged testing periods. This work establishes metallo‐polyzwitterions as a novel platform that integrates intrinsic surface affinity with tunable hydration for aqueous lubrication, overcoming the long‐standing trade‐off in aqueous lubrication.