Rate-Independent Self-Healing Double Network Hydrogels Using a Thixotropic Sacrificial Network

Tough and self-healing hydrogels can be developed by incorporating non-covalent dynamic bonds in the polymer network as reversible sacrificial bonds to dissipate energy. However, the dynamic nature of the non-covalent bonds results in strong strain rate dependency of the materials. In most applications, strain-rate independent mechanical performances are required. Developing tough self-healing hydrogels showing strain rate-independency is a challenge. In this study, we realize this by adopting the thixotropic hydrogel of an oligomeric electrolyte gelator as a brittle, though self-healing, sacrificial network of tough double network (DN) hydrogels. The hydrogels, synthesized via a facile one-pot approach, show specific features of typical double network materials, including high mechanical strength, strain softening, large mechanical hysteresis, but also self-healing and strain rate-independency. As the strain rate-independent and self-healing mechanical behavior of these novel hydrogels overcome the shortcomings of the existing DN hydrogels, these results expand the application spectrum of DN hydrogels.