POLYELECTROLYTES FROM POLYSACCHARIDES - SELECTIVE OXIDATION OF GUAR GUM - A REVISITED REACTION

The aim of this work was to study the properties of the carboxylated p olyelectrolyte obtained from guar gum. The C-6 alcohol functions of ga lactose units side chains were oxidized first by GO-ase to aldehyde gr oups and then to carboxylic groups by halogen oxidation. The enzymic o xidation step was followed by the Dische method, by viscosity and ligh t scattering measurements. With regard to previous reports, some chang es were introduced in the two-step reaction, in order to prevent polym er degradation. Several characteristics of the carboxylated polyelectr olyte have been studied, such as molecular weight distribution, degree of substitution, viscosity, intrinsic viscosity determined by the iso ionic method, radius of gyration, charge parameter and apparent intrin sic persistence length. The charged macromolecule formed from native g uar showed all the typical characteristics of a polyelectrolyte. The v iscometry results indicate that carboxylated guar has a much higher vi scosity in low salt content than the native polymer, which improves it s thickening properties.