Enhancing the self-recovery and mechanical property of hydrogels by macromolecular microspheres with thermal and redox initiation systems

In this investigation, a tough hydrogel was reinforced by macromolecular microspheres (MMs) as hydrophobic association centers via free radical polymerization with different initiation systems. The thermal initiator is potassium persulfate and the redox initiators include potassium persulfate and N,N,N′,N′-tetramethylethylenediamine (TMEDA). The mechanical measurements showed that the hydrogel with a redox initiation system possesses a tensile strength of 1.55 MPa, which is much higher than the hydrogel with a thermal initiator. Moreover, the hydrogel with redox initiators exhibited rapid self-recovery to its 90% original dimension in several seconds and low swelling property. The large difference in the morphology of hydrogels before and after swelling was due to the tight entanglement of molecular chains in the internal structure of hydrogels with redox initiators. As a result, the hydrophobic association hydrogels toughened by MMs with excellent mechanical properties would be useful for biomedical applications of tough tissue engineering, such as tendon, muscle, and blood vessel.