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.