Highly lubricious poly(vinyl alcohol)–poly(acrylic acid) hydrogels

Poly(vinyl alcohol) (PVA) hydrogels have desirable characteristics for use as artificial cartilage, such as biocompatibility, high water content, and surface lubricity. However, PVA hydrogels are not strong enough to withstand the demanding load-bearing environment in human joints. Thermal annealing can greatly improve compressive strength, but it also causes substantial loss in water content and lubricity. We demonstrated that incorporating anionic moieties of poly(acrylic acid) improves surface lubricity, whereas adding poly(ethylene-glycol) prevents pore collapse during thermal annealing, yielding a tough hydrogel with high lubricity. We also found a "super-lubricous" response from the gels when they were annealed in air versus argon gas.