Tough and Self-Recoverable Hydrogels Crosslinked by Triblock Copolymer Micelles and Fe3+ Coordination

Tough hydrogels have great potentials in soft robotics, artificial muscles, tissue replacement, and so on. Here we introduce novel tough hydrogels crosslinked by triblock copolymer (F127DA) micelles and metal coordination. The gels showed outstanding tensile strength (similar to 1-11 MPa), toughness (similar to 4-32 MJ m(-3)), and excellent self-recovery properties (similar to 56.8-87.2% toughness recovery in 9 min at room temperature). The mechanical and self-recovery properties could be manipulated by varying contents of micelles and/or COO- groups. Dynamic mechanical analysis of the hydrogels revealed apparent activation energy and relaxations for both physical interactions. In situ small-angle X-ray scattering measurements on hydrogels upon stretching revealed micelle deformations. XPS measurements on hydrogels before and after stretching revealed significant changes in the binding energy of Fe3+ ions in the gels, suggesting the rupture of coordination bonds. The experimental results strongly suggest a synergistic effect from the micelle-crosslinking and Fe3+-COO- coordination on the strength, toughness, and self-recovery of the hydrogels. (C) 2018 Wiley Periodicals, Inc.