Evaluation of viscometric properties of carboxymethylcellulose and gellan

Viscometry is an inexpensive characterization method to obtain important information about the hydrodynamic volume and conformation of polymers in diluted solutions, in a determined solvent and specific temperature. The viscometric parameters can be mathematically calculated by graphical extrapolation or single-point determination. This article reports a viscometric study of two polysaccharides, carboxymethylcellulose (CMC) (degree of substitution = 2.23) and gellan (GL), with the use of two calculation methods, employing a series of six equations: Huggins, Kraemer and Schulz-Blaschke, by graphical extrapolation; and Schulz-Blaschke, Solomon-Ciuta and Deb-Chanterjee, by single-point determination. It is also used Wolf equations for a different way to determine the intrinsic viscosity. The solution for CMC analyses was NaCl 0.2 mol/L, and for gellan determination, the solvent applied was KCl 0.1 mol/L. For both polymers, the test temperature was 30 ± 0.1 °C. The average molar mass was also determinate by the viscometry analysis. The values of intrinsic viscosity of some constants indicated that the solvents systens used for CMC and for gellan, the solvents used are classified as a good system (kh + kk < 0.5). It was also observed that the method of calculation by a single-point determination was valid for both polyelectrolytes analyzed.