writer：Jia Yang, Lin Zhu, Xiaoqiang Yan, Dandan Wei, Gang Qin, Baozhong Liu, Shuzheng Liu, Qiang Chen
keywords：Nanocomposite Hydrogel; Hybrid; Energy Dissipation; Self-recovery; Self-healing
source：期刊
specific source：RSC Adv
Issue time：2016年

Polymer nanocomposite hydrogels (NC gels) have been intensively investigated for applications in academic and industrial fields. In the present work, hybrid cross-linked polyacrylamide (PAAm)/Laponite hydrogels were  synthesized by in situ free radical polymerization using Laponite nanoplatetes and N,N-methylenebisacrylamide (MBA) as physical and chemical crosslinkers, respectively. We aimed to make it clear the synergistic effect of physical and chemical crosslinkings on the mechanical properties, self-recovery, fatigue resistance and self-healing performances of hybrid PAAm/Laponite NC gels. The effects of Laponite and chemical crosslinker concentration on mechanical properties of the physical and hybrid NC gels are investigated in details. It was found the fracture stress and fracture energies of hybrid NC gels decreased sharply as chemical crosslinker (MBA) concentration was larger than 0.05 mol% of monomer. With a very small amount of chemical crosslinkers, the hybrid NC gels exhibited improved tensile properties, large hysteresis and good self-recovery performances. The best tensile properties of hybrid NC gels in this study were σf of 0.45 MPa, εf of 50.63 mm/mm, E of 72.64 kPa and W of 9.81 MJ/m3, which were much better than those of physical NC gel and pure chemical gel. However, it was also revealed there was negative effect of chemical crosslinking on the fatigue resistance and self-healing properties of NC gels. A deformation and recovery mechanism was also proposed. We believe this work will provide better understanding about the relationship of network structure and properties for hybrid NC gels.