Failure Behavior of Alginate Hydrogels

Polysaccharide networks are widely used in biomedical and food applications. In this presentation, results on alginate hydrogels, a model polysaccharide network, will be presented. Alginate gels with two different types of crosslinking, ionic and covalent, are considered. Calcium salts have been used to obtain ionically crosslinked gels. Diamines and amine functionalized carbon nanodots have been used to synthesize covalently crosslinked gels. Small angle x-ray scattering captures the structural differences in ionic and covalently crosslinked gels. These gels display strain stiffening behavior in shear-rheology. A custom built cavitation rheology technique was used to capture the failure behavior of these gels. Here, at the critical pressure, instead of a spherical cavity growth at the needle tip, fracture in gel has been observed. The critical pressure changes with the type of crosslinking and as a function of crosslinker concentration. The fracture propagation has been found to be different in the ionic and covalently crosslinked gels.