Tribological properties of zwitterionic-anionic dual-crosslinked P(AAm-co-AAc-co-SBMA-co-AMPS)/Fe3+ hydrogel

Hydrogel is an ideal material for cartilage repair, but it is difficult for artificial materials to achieve ultra-low friction coefficient of cartilage at present. The amphoteric ion anionic double crosslinked P(AAm-co-AAc-co-SBMA-co-AMPS)/Fe3+hydrogel was synthesized by using the amphoteric monomer [2-(methacryloxy) ethyl] dimethyl-(3-sulfopropyl)(SBMA) and the anionic monomer 2-acrylamido-2-methylpropane sulfonic acid (AMPS). The frictional tests were conducted in water and PBS to evaluate the effects of zwitterionic and anionic groups on the coefficient of friction (CoF). The results show that the physical crosslinking point introduced by SBMA and AMPS can improve the compressive strength of hydrogel, and achieve a low CoF (0.04) in water, In addition, it is observed that CoF further decreases to 0.015 in PBS, and the decrease of CoF is caused by the highly hydrated upper layer of hydrogel produced during PBS soaking.