Ultrastretchable, Self-Healable Hydrogels Based on Dynamic Covalent Bonding and Triblock Copolymer Micellization

Excellent mechanical properties and remarkable self-healing ability are difficult to unify in one hydrogel. We integrated acylhydrazone bonds and Pluronic F127 (PF127) micelle cross-linking, as two kinds of dynamic cross-links, in one system and developed hydrogels with superior stretchability, high toughness, and good self-healing ability. The hydrogel could stretch up to 117 times its initial length and self-heal approximately 85% of its initial strength within 24 h. The toughness of the hydrogel, indexed by the work of extension, W, reached 14.1 MJ m(-3). Energy dissipation occurred from the simultaneous decomposition of the PF127 micelles and chain sliding facilitated by the reconfiguration of the acylhydrazone bonds. This unique combination and dynamics led to pronounced hysteresis in the loading unloading cycles, as well as good recovery and self-healing of the hydrogel. Dynamic cross-linking of the covalent acylhydrazone bonds was comparable to those of physical interactions, such as coordination and ionic bonding.