Stimuli-Responsive Supramolecular Hydrogels with High Extensibility and Fast Self-Healing via Precoordinated Mussel-Inspired Chemistry

Supramolecular hydrogels have the advantages of stimuli responsiveness and self-healing compared to covalently cross-linked hydrogels. However, the existing supramolecular hydrogels are usually poor in mechanical properties, especially in extensibility. In addition, these supramolecular hydrogels need a long self-healing time and have a low self-healing efficiency. In this manuscript, we report a novel strategy to develop highly extensible and fast self-healing supramolecular hydrogels by using precoordinated mussel-inspired catechol-Fe³⁺ complexes as dynamic cross-linkers. The hydrogel can be fabricated and cast into various shapes by one-step photo-crosslinking. Thus, fabricated hydrogels can be stretched beyond 10 times their original lengths, and the high extensibility can completely recover within a very short time (less than 20 min) even after the hydrogels are entirely cut apart. Utilizing the dynamic nature of supramolecular hydrogels, we can realize different mechanical behaviors, including strength, extensibility, and recoverability by varying the loading conditions. In addition, the hydrogels respond to multiple stimuli, including mechanical force, temperature, and certain chemicals because of the dynamic catechol-Fe³⁺ bond.