High-strength and tough composite hydrogels reinforced by the synergistic effect of nano-doping and triple-network structures

Developing composite hydrogels with superior compressive mechanical performances attracted wide attention in recent years. In this work, a novel designing strategy was proposed to prepare a GOs/Fe³⁺-CMC/PVA triple-network (TN) hydrogel by a simple three-step procedure, including chemical polymerization, metal ionic coordination, and repeated freezing/thawing cyclic. The microstructures, functional groups, and elements distribution of the composite hydrogels were characterized by High resolution scanning electron microscope (HRSEM), Fourier transform Infrared (FTIR) and Energy dispersive X-ray (EDX) analysis, respectively. Furthermore, the compressive mechanical properties of the hydrogels with different mass ratios of GOs/PVA (0.4% ~2.0%), CMC/PVA (0.04~0.20), and freezing/thawing cyclic numbers (0, 5, & 9 times) were evaluated, respectively. The synthetic TN composite hydrogels with optimized compositions exhibited excellent mechanical strength (5.366 ± 0.58 MPa) and toughness (617.4 ± 39 kJ/m³). Besides, the as-prepared composite hydrogels owned rapid recovery and fatigue resistance abilities. More importantly, it has analyzed the specific toughening role of each network during the energy dissipation process. The designing strategy may provide a new idea for developing high-strength and tough TN hydrogels and understanding their toughening mechanisms.