Abstract:

A double network hydrogel was constructed by using natural polysaccharide sodium alginate and acrylamide as monomers， and chitosan was introduced to enhance the mechanical toughness of the hydrogel. The morphology， network crosslinking structure， and thermal properties of the as⁃prepared hydrogel were characterized by using scanning electron microscopy， infrared spectroscopy， X⁃ray diffraction， and synchronous thermal analysis， and its crosslinking mechanism was analyzed. The results indicated that the toughness of the hydrogel was improved with an increase in the chitosan content. The increase of toughness at a low chitosan content was caused by the increase of elongation ability， whereas its increase at a high chitosan content it was caused by the simultaneous increase of strength and elongation. The toughness value of the hydrogel with 10 wt% chitosan reached 2.50×10⁵ kJ/m³， which was significantly higher than the hydrogel containing 5 and 7.5 wt% chitosan. The elastic recovery rate of the hydrogel decreased with an increase in the set elongation rate during the constant elongation cycle stretching， and it was higher than 98 % at set elongation of 25 %， but only higher than 90 % at set elongation of 200 %. The hydrogel with 10 % chitosan exhibited the best elasticity with a strong fracture stress of 0.249 MPa and fracture elongation of 1 635.65 %， and it presented an excellent recovery ability at a constant elongation cycle of 200 % or less. This study can provide a solution for the toughening of hydrogels.

Key words: sodium alginate, polyacrylamide, double?network hydrogel, chitosan, mechanical property