Fatigue-Resistant, Notch-Insensitive Zwitterionic Polymer Hydrogels with High Self-Healing Ability

Graphical Quick and strong : Self-healing hydrogels were synthesized by random copolymerization of the three monomers. The reversible ionic bond formed between the monomers effectively enhanced the degree of cross-linking of the polymer network, thus furnishing the hydrogels with excellent mechanical and self-healing properties, which can be produced in a short time. The strain energy dissipation of reversible ionic bonds enhanced the fatigue resistance of the hydrogels and made them notch-insensitive. Introducing self-healing properties into hydrogels can prolong their application lifetime. However, achieving mechanical strength without sacrificing self-healing properties is still a major challenge. We prepared a series of zwitterionic polymer hydrogels by random copolymerization of zwitterionic ionic monomer (SBMA), cationic monomer (DAC) and hydrophilic monomer (HEMA). The ionic bonds and hydrogen bonds formed in the hydrogels can efficiently dissipate energy and rebuild the network. The resulting hydrogels show high mechanical strength (289–396 KPa of fracture stress, 433–864 % of fracture stress) and have great fatigue resistance. The hydrogel with a 1 : 1 molar ratio of SBMA:DAC possesses the best self-healing properties (self-healing efficiency up to 96.5 % at room temperature for 10 h). The self-healing process is completely spontaneous and does not require external factors to assist. In addition, the hydrogel also possesses notch insensitivity with a fracture energy of 12000 J m −2 . After combining the conductivity of RGO aerogel, the hydrogel/RGO composites show good strain sensitivity with high reliability and self-healing ability, which has certain significance in broadening the application of these zwitterionic hydrogels.