Conformational studies of carboxymethylcellulose in aqueous saline solutions as a function of ionic strength

The conformation of carboxymethylcellulose (CMC) in salt solutions was studied using viscometry, light scattering and gel permeation chromatography. From the viscosity data, the conformation of CMC in aqueous saline solutions was determined to be elliptical. At high ionic strengths, for example 2.5N NaCl, the macromolecule collapses upon itself. The gel permeation chromatography data indicated the presence of large molecular weight CMC particles (~2 x 109 daltons). The light scattering data also showed the presence of large CMC particles. The presence of large CMC particles explains the change in concentration dependence of the viscosity data between low and high CMC concentrations. Two species in solution, CMC molecules and CMC aggregates, each contribute to the observed viscosity. Both CMC molecules and aggregates, at low concentrations, show a linear relationship between viscosity and concentration, however, the slopes of the lines are different. A model is cited which provides an explanation of the viscous behavior of CMC in distilled water and salt solutions over time, based on solvation of CMC aggregates. This research suggests that the solvation time can be greatly reduced by autoclaving the solutions, thereby achieving an equilibrium viscosity