Flexible Polysaccharide Hydrogel with pH-Regulated Recovery of Self-Healing and Mechanical Properties

A self-healable hydrogel with recoverable self-healing and mechanical properties is reported. The hydrogel (coded as ACSH) crosslinked by Schiff base linkage contains two polysaccharides of acrylamide-modified chitosan (AMCS) and oxidized alginate (ADA). Self-healing and mechanical properties are heavily influenced by the crosslinking time. The hydrogel crosslinked for 2 h possesses better mechanical and self-healing properties than hydrogel crosslinked for 24 h. Macroscopic test shows that hydrogel without self-healing ability can recover the self-repair and mechanical properties by adjusting the pHs. The recovery of self-healing and mechanical properties relies on the pH sensitivity of the Schiff base linkage. Adjusting the pH to acid, the Schiff base linkage becomes unstable and breaks. Regulating the pH to neutral, reconstruction of Schiff base linkage leads to recovery of the self-repair and mechanical properties. The recoverable self-healing property can be cycled once breakage and reconstruction of the Schiff base linkage can be conducted. In addition, this study demonstrates that the hydrogel can be remodeled into different shapes based on self-healing property of the hydrogel. It is anticipated that this self-healable hydrogel with recoverable self-healing and mechanical properties may open a new way to investigate self-healing hydrogel and find potential applications in different biomedical fields.