Preparation and characterization of carboxymethylcellulose based hydrogels

Carboxymethylcelusose (CMC) based hydrogels were synthesized by crosslinking methot in presence of poly(vinylalcohol) (PVA) and fumaric acid (FA) used as a crosslinker. NaCMC and PVA cross-linked with different concentrations of FA. Hydrogels were characterized with different methods (FTIR, TGA, XRD and SEM) of analysis. The water absorbencies of these hydrogels in different pH solutions were investigated. As the FA concentration was increased, equilibrium swelling capacity reduced due to increasing crosslinking between CMC and PVA. Also pH sensitivity and reversibilty of hydrogels were investigated. The results indicated that the hydogels in the base medium had higher swelling behavior than the acidic medium. More over the hydrogels had pH reversibilty behavior which swelled at pH=8 and shrinked at pH=2.6. The FTIR results indicated the cross-linking between carboxyl group of FA with hydroxyl group of PVA and NaCMC through ester formation. The thermal behavior of the hydrogels was examined by TGA/DTG. The crosslinking improved the thermal stability of the hydrogels. Furthermore the SEM analysis showed that a highly porous structure was observed for 10FA and 15FA hydrogels while for 20FA and 25FA samples firstly high fibrous structure, then dispersion was observed.