Autonomous Chitosan-Based Self-Healing Hydrogel Formed through Noncovalent Interactions

A facile strategy was developed for the formation of an autonomous chitosan-based self-healing hydrogel. This hydrogel was fabricated using in situ free radical polymerization of acrylic acid (AA) and acrylamide (AM) in the presence of chitosan in dilute acetic acid aqueous solution under mild conditions. The in situ formed hydrogel is mainly composed of chitosan graft copolymers (CS-g-P(AM-r-AA)) and a small amount of nongrafted copolymers (P(AM-r-AA)), which interact with each other through a combination of multiple noncovalent interactions, including the interchain electrostatic complexation between -[AA]- segments and positively charged amino groups of chitosan, the H-bonding between -[AM]- segments, and the H-bonding between -[AM]- segments and the chitosan backbone. Owing to the cooperation of these noncovalent interactions and the reversible nature of the noncovalent network structure, the obtained hydrogel exhibits rapid network recovery, high stretchability, and efficient autonomous self-healing properties. The hydrogel can also dissolve completely in dilute acidic aqueous solution under mild conditions, visibly reflecting the unique network feature of this self-healing hydrogel system.