Hydration Lubrication Applicable to Artificial Joints through Polyelectrolyte-Embedded Modification on UHMWPE

Hydration lubrication by the hydrated surface-grafted macromolecules covering the joint cartilage is crucial for the proper functioning of natural synovial joints. However, when considering artificial replacements, similar surface-grafted polymers on artificial materials are usually insufficient for the long-term lubrication due to lack of stability and durability. In this work, an overall material modification through embedding polyelectrolyte brushes was performed for prolonged lifetime. Method-wise, hydrophilic monomer 3-sulfopropyl methacrylate potassium salt (SPMK) was grafted onto ultrahigh molecular weight polyethylene (UHMWPE) powders through photoinduced radical graft polymerization, followed by hot-press forming of the modified powders to afford homogeneous modified material. Trials revealed significantly increased surface wettability and negative charge density, giving rise to strong hydration lubrication that led to a stable and low friction coefficient of 0.009, and an ultralow wear rate of 9.1 × 10–8 mm3 (N m)−1 under physiological conditions, which could be consistently maintained even after the surface was sheared off with polishing equipment. This overall material modification on UHMWPE through polyelectrolyte embedment, applied to obtain long-lasting, highly lubricated materials, therefore presents a promising method for the preparation of artificial joints.