PVA/silica hybrid hydrogel with ultra-high strength and toughness

Due to the good biocompatibility, polyvinyl alcohol (PVA) hydrogels have attracted the attention of many biomaterial researchers. However, the low strength and poor toughness of pure PVA hydrogel prepared by freeze–thaw method limit the application. In this study, silica was used to enhance the performances of PVA hydrogel. Different from previous PVA/SiO₂ hydrogels, urea was used to regulate the formation and distribution of silica in PVA, which greatly improved the mechanical properties of hydrogels. The tensile stress and toughness of the obtained PVA(Urea)/SiO₂ hydrogels reached 8.10 MPa and 44.45 MJ/m³, which were 39 times and 212 times as that of pure PVA hydrogel, respectively. In PVA(Urea)/SiO₂ hydrogels, SiO₂ had both strengthening and toughening effects on hydrogels, which is very different from the ordinary composite hydrogels. In addition, PVA(Urea)/SiO₂ hydrogels showed unique self-reinforcing characteristics with increasing the number of tensile recoveries in cyclic stretching and recovery tests. Thus, PVA(Urea)/SiO₂ hydrogel with high strength and toughness, constructed by a simple strategy, is a potential candidate in cartilage repair.