A novel dual crosslinked polysaccharide hydrogel with self-healing and stretchable properties

In the context of providing better stability and enhancing the mechanical properties of natural polysaccharides, self-healing hydrogels have attracted much attention because of their ability to spontaneously repair after damage. In this study, cellulose was modified to improve its solubility and cellulose acetoacetate (CAA) was obtained. Immediately, the acetoacetyl group of CAA reacts with the amine group of carboxymethyl chitosan (CMC) to generate enamine linkages, which formed the hydrogel (CAA/CMC) with self-healing capacity. Furthermore, to enhance the strength and accelerate the self-healing rate of the CAA/CMC hydrogel, CAA was oxidized to form dialdehyde groups and then reacted with CMC and oxalyl dihydrazide (ODH) to produce an enamine and acylhydrazone connected complex hydrogel (CMC/OCAA), a novel dual dynamic covalent bond crosslinked polysaccharide hydrogel. The mechanical and rheological properties of the hydrogels were investigated with different volume ratios of CMC. As the ratio of CMC and OCAA was 4 : 1, the tensile strength and storage modulus of the OCAA composite hydrogel increased to 242 kPa and 17.07 kPa from 15 kPa and 1.50 kPa of the CAA hydrogel. The self-healing time of the OCAA hydrogel reduced to 30 min compared with that of the CAA hydrogel of 12 h. Moreover, the cyclic tensile results demonstrated that the CMC/OCAA hydrogel exhibited very good fatigue resistance with 83.3% self-healing efficiency after self-healing for 48 h, much higher than 58.4% of the CMC/CAA hydrogel. Together with the existence of blood compatibility, cytocompatibility, and antibacterial and antioxidant properties, the complex hydrogel is highly attractive for biomedical, controlled release, and other applications.