Nanocomposite interpenetrating hydrogels with high toughness and good self-recovery

It is particularly desirable to fabricate highly tough hydrogels with excellent self-recoverable properties for applications where high stress is required. In this work, we prepared a tough, fast self-recoverable nanocomposite hydrogel by chemical cross-linking of acrylamide (AM) monomers with vinyl-modified silica nanoparticles (VSNPs), combined with physical cross-linking of polyvinyl alcohol (PVA). The uniaxial tensile test showed that the nanocomposite hydrogel has excellent mechanical properties. The maximum elongation at break was as high as 666%, and the tensile strength was as high as 1.68 MPa. Cyclic loading-unloading tests revealed the excellent self-healing properties of the nanocomposite hydrogel. It is worth noting that the nanocomposite hydrogel exhibited higher strength after two loading-unloading cycles, due to the orientation of the PVA when stretched. In addition, the effects of PVA, VSNPs, and AM concentrations, and the number of PVA freeze-thaw cycles and freezing duration on the mechanical properties of the hydrogels were investigated in detail.