Synthesis and Properties of Highly Swelling PAAm/Chitosan Semi‐IPN Hydrogels

Abstract A semi‐interpenetrating polymer network (semi‐IPN) hydrogel composed of crosslinked chitosan and polyacrylamide (PAAm) was prepared in the presence of formaldehyde as a crosslinker. The swelling capacity of hydrogel was shown to be affected by the crosslinker and the PAAm/chitosan ratio. The PAAm/chitosan semi‐IPN hydrogels are swelled at low pHs that attributed to both osmotic pressure and repulsion of NH groups on chitosan backbones. The swelling of hydrogel in acidic pHs showed that with increasing of chitosan content in the hydrogel, the swelling capacity was increased. But the swelling capacity of hydrogel in neutral pH is reversed, i.e. the higher the PAAm/chitosan ratio, the higher the swelling capacity. The results also indicated that the semi‐IPN hydrogel had different swelling capacity in various pHs. It showed a reversible pH‐responsive behavior at pH 2 and 10.