Preparation and characterization of N -isopropylacrylamide/carboxymethylated chitosan hydrogel

Poly (N-isopropylacrylamide) (PNIPAAm)/carboxymethylated chitosan (CMCH) hydrogels were prepared by irradiating the aqueous solution mixture of NIPAAm and CMCH by 60Co γ-ray. The effects of feed ratio of NIPAAm and CMCH, temperature, pH and ionic strength on the swelling ratio of PNIPAAm/CMCH hydrogels were studied. The results show that the addition of CMCH shifts the lower critical solution temperature (LCST) of the PNIPAAm hydrogel to higher temperature. The PNIPAAm/CMCH hydrogel displays not only pH- and thermo- sensitivity, but also ion-sensitivity. Differential scanning calorimetry (DSC) was applied for the determination of the LCST of the hydrogel.