Swelling behavior of semi-interpenetrating polymer network hydrogels based on chitosan and poly(acryl amide)

Semi-interpenetrating polymer networks (semi-IPNs) composed of chitosan and polyacrylamide (PAAm) hydrogels have been prepared, and the effect of changing pH, temperature, ionic concentration, and applied electric fields on the swelling of the hydrogels was investigated. The swelling kinetics increased rapidly, reaching equilibrium within 60 min. The semi-IPN hydrogels exhibited a relatively high swelling ratios of 385%-569% at T = 25 degrees C. The swelling ratio increased with decreasing pH below pH = 7 due to the dissociation of ionic bonds. The swelling ratio of the semi-IPN hydrogels was pH, ionic concentration, temperature, and electric field dependent. Differential scanning calorimetry (DSC) was used to determine the volume of free water in the semi-IPN hydrogels, which was found to increase with increasing PAAm content.