Tough, high-strength PDAAM-co-PAAM hydrogels synthesized without a crosslinking agent

Hydrogels find a variety of uses across various fields, but their development might be limited by their high-cost, toxic chemical crosslinking and complicated reactions. To address these issues, we developed a tough, high-strength hydrogel of polydiacetone acrylamide-co-poly(acrylamide), prepared using acrylamide, diacetone acrylamide (DAAM) and ammonium persulfate in a one-step reaction. The multiple physical crosslinking networks endow hydrogel with excellent overall properties given appropriate DAAM levels. The tensile modulus, fractured strain, fractured stress and toughness of the developed D₁A₉ hydrogel are, respectively, as high as 0.15 MPa, 21 mm/mm, 0.71 MPa and 7 MJ/m². Its compressive modulus under a strain of 80% is 0.088 MPa, while its shear modulus at a shear frequency of 100 Hz is 0.071 MPa. At the same time, D₁A₉ hydrogel exhibits a high self-recovery efficiency of 50% during two continuous cyclic tensile tests, with the efficiency increasing to 65% for hydrogel incubated at 50 °C for 2 h. Finally, cytocompatibility and excellent drug-releasing behavior of the hydrogel make it a candidate for biomedical use.