title: Influence of ionic strength and polyelectrolyte concentration on the electrical conductivity of suspensions of soft colloidal polysaccharides.
abstract: The electrokinetic properties of carboxymethyldextran, a soft and anionic polysaccharide, were analysed in aqueous NaNO3 solutions through measurements of the electrical conductivity of the suspensions. The results, which furnish new experimental support for the structure of soft polysaccharides in electrolyte solution show that the polyion concentration governs the conductance behavior of the suspension as the ionic strength decreases. This is particularly evident for large polymer concentrations, for which electrical double layer overlap is more likely. In contrast, the electrical conductivity of the suspension at high ionic strength reduces to the contribution of the ions in solution, as screening of the polyion charges is more efficient in such conditions. The applicability of Ohshima's general conductivity expression to these electrical conductivity measurements was examined, and a major discrepancy against the theory was observed. The calculated values of the electrical conductivity deduced on the basis of this theory were found to be lower than the experimental ones. Possible reasons for this discrepancy are discussed and a numerical model, based on the use of a cell approach to account for hydrodynamic and electrical interactions between particles, has shown to be a good description of the experimental electrokinetic data.
authors: Laboratoire de Chimie des matériaux Inorganiques, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Abidjan, Cote d'Ivoire.
authors: Jean-Pierre S
authors: JS
authors: Sagou
authors: Department of Applied Physics, School of Science, University of Granada, 18071 Granada, Spain. Electronic address: sahualli@ugr.es.
authors: Silvia
authors: S
authors: Ahualli
authors: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360 CNRS-Université de Lorraine, 15 Avenue du Charmois, 54000 Vandoeuvre-lès-Nancy, France.
authors: Fabien
authors: F
authors: Thomas
authors: Jérôme F L
authors: JFL
authors: Duval
mesh_terms: D003102:Colloids; D003911:Dextrans / Q000737:chemistry*; D004553:Electric Conductivity; D009566:Nitrates / Q000737:chemistry*; D009994:Osmolar Concentration; D011134:Polysaccharides
chemical_list: D003102:Colloids; D003911:Dextrans; D009566:Nitrates; D011134:Polysaccharides; C031618:sodium nitrate; C014392:carboxymethyl dextran
keywords: Carboxymethyldextran; Electrical conductivity; Overlapping; Polyion–polyion interactions; Soft particles