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.