The Ultra Lubricating Behavior Of Hybrid Cross-linked Hydrogel With High Strength

The complicated environment of human body put forward high requirement on biomaterials' peformances for their biomedical applications,especially on the biocompatibility,mechanical strenghth and lubrication.With the development of biomaterials,a variety of specifically designed products of artificial tissues have been explored for several decades,some of which are already available in the marketplace and routinely used in clinical treatments.Hydrogel is a desired candidate for natural human soft tissue for the polymer networks swollen with large amounts of water,which the same as bio-tissue.The lacking of mechanical strength has long been a limit for hydrogels' application until the double network?DN?hydrogel which has excellent mechanical performance was proposed.Our research based on the concept of double network,synthesized two hydrogels: Polyvinyl alcohol/ sodium alginate?PVA/SA?,polyacrylamide/ sodium alginate?PAAm/SA?to explore the toughening mechanism,slef-healing properties and friction performance of PVA/SA.We also discussed the effect of ionic solutions to PVA/SA and PAAm/SA hydrogel.The PAAm/SA hydrogel exhibits an excellent elongation and high strength properties.The sample of PVA/SA can be stretched to 5 times its original length before ruptured,the PVA/SA gel achieves the highest tensile stress of 1.9 MPa,the toughness of PVA/SA achieves 4461 k J/m3.We successfully prepared a high strength hydrogel.As the ionic cross links can rebuilt,in the rheology tests,PVA/SA shows good mechanical recovery,the mechanical strength can immediately recovers to almost 100% of the initial value after structure breakdown.While the PVA/SA hydrogel soaked in Ca²⁺ ionic solutions after a certain strain.The Yong's modulus can recovery to about 90% of that of the first loading,the dissipated energy can recovery to 75%.PVA/SA hydrogel has a strong attractive effect with glass substrate because of the attractive effect of PVA with galss.PAAm/SA is fabricated and the elasticity modulus,swelling ratio and frictional behavior of PAAm/SA immersed in Na+,Ca²⁺ and Fe³⁺ was measured.The elasticity modulus of PAAm/SA in Fe³⁺ ionic solutions is 126 k Pa which is 14 times of the PAAm/SA immersed in water.The frictional stress of PAAm/SA hydrogel significantly decreases over the entire range of sliding-velocity contrast to PAAm.The frictional stress of SA and PAAm/SA increased with the valences of ionic.When the solution turn from Ca²⁺ to Fe³⁺,the friction mechanism of PAAm/SA shift from mixed lubrication to boundary lubrication.Moreover,the sensitivities about the friction stress of PAAm/SA in Fe³⁺ to stress decrease with the slip rate increase.