Synthesis and characterization of multi-sensitive microgel-based polyampholyte hydrogels with high mechanical strength

In this study, multi-sensitive hydrogels with high mechanical strength were successfully prepared by in situ free-radical polymerization of acrylamide, acrylic acid and acryloyloxyethyl trimethyl ammonium chloride monomers in the presence of microgels in aqueous media. Microgels with amine groups on the surface were used as polyfunctional initiating and cross-linking centers to fabricate a network. The microgel-based hydrogels synthesized did not fracture upon loading up to 30 MPa and a strain above 99 % when the water content was about 84 wt%. As for the swelling behaviors of the microgel-based hydrogels, they were susceptible to pH and salt concentration. Meanwhile, deswelling tests indicated that the microgel-based hydrogels had thermo-sensitive properties and under high temperature exhibited a faster shrinking rate, which could be attributed to the solvent channels caused by the shrinkage of microgels due to their thermo-sensitive core. And microgel-based hydrogels with various deswelling rates can be determined by regulating the content and species of microgel. Furthermore, the low extensibility of microgel-based polyampholyte hydrogels could be improved by creating a hybrid network with microgels and a small amount of N,N’-methylenebisacrylamide served as the chemical cross-linkers. The hybrid hydrogels possessed superior compressive strength and simultaneously showed abnormal elongation of up to 1000 %.