Rheological and Swelling Behavior of pH Sensitive Hydrogel Particles

pH sensitive hydrogel particles were characterized for their rheological and swelling behaviour at various pH values specific to the gastrointestinal tract simulated conditions. Scanning electron microscopy was used to view the surface morphology of the hydrogels at different pHs. Swelling at pH 7.4 and shrinkage at pH 1.2 confirmed the pH sensitive behaviour of the hydrogel particles. The Linear Viscoelastic (LVE) range was determined by considering G’, one of the strain amplitude. Furthermore frequency sweep tests were performed in the LVE range where the storage modulus and loss modulus were determined at constant strain. It was observed that the loss modulus was higher at basic pH while the storage modulus was higher at lower pH. This rheological method can be used to explain the pH sensitive behaviour of hydrogels.