Synergistic toughening of nanocomposite hydrogel based on ultrasmall aluminum hydroxide nanoparticles and hydroxyapatite nanoparticles

The development of hydrogels combining superior mechanical property attracts researchers' attention in recent years. Here, a novel nanocomposite hydrogel is prepared by one-step photo-polymerization of acrylic acid (AA) and N,N-dimethylacrylamide (DMAA) in the presence of hydroxyapatite nanoparticles (HAp NPs) and aluminum hydroxide nanoparticles (Al(OH) ₃ NPs). The resulting transparent hydrogel exhibits ultrahigh toughness of 28.3 MJ m ⁻³ , high strength of 2.8 MPa, large elongation of 1300%, excellent self-recovery and good biocompatibility. The crosslinking mechanism is contributed to the ionic coordination interaction between cations absorbing on the surface of nanoparticles and carboxyl groups of the polymer chain, and the synergistic toughening effect between HAp NPs and Al(OH) ₃ NPs is responsible for improving the strength and toughness simultaneously. Furthermore, this synergistic toughening strategy may provide a universal method for designing and constructing high strength nanocomposite hydrogels in many applications, especially for artificial cartilages. POLYM. COMPOS., 40:942–951, 2019.