Enhanced Hydration Lubrication of Ultrahigh Molecular Weight Polyethylene/Halloysite Nanotubes Composites with Embedded Polymer Brushes

Osteoarthritis, a degenerative joint disease affecting hundreds of millions of people worldwide, leads to chronic pain and reduced mobility, for which total joint arthroplasty remains the definitive and most effective treatment. Ultrahigh molecular weight polyethylene (UHMWPE) has been the most widely used bearing material in artificial joints owing to its excellent tribological properties and biocompatibility. However, the long-term clinical outcome of this treatment is limited by the wear-induced failure of UHMWPE implants. Inspired by the natural joint's lubrication mechanism, a bulk grafting modification strategy was adopted to fabricate a bio-lubricating UHMWPE composite with an extended service life. Hydrophilic anionic polymer brushes poly(3-sulfopropyl methacrylate potassium salt) (PSPMK) were grafted onto UHMWPE powder via photo-induced polymerization, while halloysite nanotubes (HNTs) were similarly modified to enhance dispersion and interfacial synergy. The composite with 1 wt % modified HNTs exhibited a remarkably low coefficient of friction (0.012) and wear rate (8.98 × 10-7 mm3·N-1·m-1), representing reductions of 52.9% and 66.2%, respectively, compared to pristine UHMWPE. Mechanical properties, including compressive strength, modulus, and hardness, were also improved due to the reinforcing effect of well-dispersed HNTs. The integrated PSPMK brushes embedded throughout the bulk material ensure persistent hydration lubrication even after surface wear. This work provides a promising material design for next-generation long-lasting artificial joints with combined high strength and superior lubrication.