Preparation And Study On Tribological Properties Of Biomimetic Self-lubricating Pvabased Hydrogels

Articular cartilage is a dense but highly hydrated load-bearing connective tissue that covers the surface of the long bones in synovial joints,acts as a cushion to absorb shocks,and allows bones to slide relatively in a nearly frictionless manner.However,mature cartilage tissue does not contain blood vessels and nutrients,and cannot repair itself after being damaged.Traditional cartilage repair methods have major limitations and cannot restore the biological integrity and functions of natural tissues,and may lead to further complications.Hydrogel is considered to be the most promising substitute for bionic articular cartilage.It is a polymer with a three-dimensional network structure prepared with water as a swelling agent and has a structure similar to natural articular cartilage.The network structure of the hydrogel is composed of the main chain of macromolecules and the side chains containing hydrophilic(polar)groups and hydrophobic groups or dissociative groups,which are easy to modify to make it show the required Mechanical properties and lubrication properties.In this experiment,the modification of PVA-based hydrogels was carried out through the functional and structural bionic design of natural articular cartilage.We characterized the structure and microscopic morphology,analyzed the hydrophilicity and swelling properties of the composite hydrogel,and tested the friction and mechanical properties of the hydrogel.First,the zwitterionic betaine MPDSAH was added by blending,and the zwitterionic was used to adsorb synovial fluid to form a hydration layer,which effectively improved the lubricating performance of the PVA hydrogel.The PVA-MPDSAH double network hydrogel was prepared by ultraviolet irradiation and physical cross-linking,which further improved the mechanical properties of the hydrogel.By adjusting the content of MPDSAH or the time of UV irradiation,the friction coefficient of PVA hydrogel could be reduced by one time,and its mechanical properties could be increased by more than 40 times.Secondly,to simulate the structure of "cartilage-subchondral bone" to prepare soft and hard bonding samples,we used polyetheretherketone(PEEK)as a hard substrate,and used concentrated sulfuric acid to sulfonate PEEK.The surface presented a three-dimensional structure with holes and the structure of PEEK was not changed.Combining PVA-MPDSAH composite hydrogel as a lubricating layer with ultraviolet radiation or casting drying on the surface could improve the wettability,hydrophilicity and tribological properties of the hard substrate.The surface layer of the hydrogel prepared by ultraviolet radiation has a higher degree of cross-linking and stability,and it exhibited good wetting and friction properties,and could maintain stable low friction during long-term friction tests.The hydrogel layer prepared by casting and drying had better hydrophilic properties,exhibited better self-lubricating properties during friction,and exhibited a smaller friction coefficient.In experiments,it was found that both sulfonation treatment and ultraviolet light irradiation of PEEK could improve the bonding strength of the hydrogel layer and the hard substrate.