Swelling behavior of carboxymethylcellulose hydrogels in relation to cross-linking, pH, and charge density

Hydrogels of carboxymethylcellulose (CMC) with 2.5%, 25%, 50%, and 100% cro ss-linking were prepared. Cross-linking and stoichiometry was controlled by appropriate addition of CMPJ and determined by potentiometric titration. T he cross-linked polymer was then sulfated using a sulfur trioxide-pyridine complex (SO3-Py) in a heterogeneous mixture. Water uptake of the gels was s tudied in relation to cross-linking, pH, and sulfation. FT-IR spectra of th e gels were recorded at different pHs to evidence the hydrogen bonds. Hydro gen bonds formation between the chains may explain the correlation found be tween water uptake properties and the chemical composition of the gels.