pH mediated rheological modulation of chitosan hydrogels.

Chitosan (CS) hydrogels are used widely for multifarious applications in diverse fields due to the property of pH responsiveness. This study aims to explain the sensitivity of CS hydrogels to alteration in pH due to change in the concentration of acetic acid, which is a solvent for CS. Studies on changes in rheological properties in this regard are still scarce. The present study evaluated the change in rheological properties of the CS hydrogels by studying the flow behaviour, creep recovery and thixotropic property. The obtained data were used to fit mathematical models, like power law model and Herschel-Bulkley model to gain a vivid understanding of the rheological properties of CS hydrogel. Overall analyses revealed that the CS hydrogels, irrespective of the pH, were highly elastic in nature and exhibited significant creep recovery. However, the steady flow behaviour and thixotropy varied substantially with variation in pH.