Influence of temperature, added electrolyte, and polymer molecular weight on the counterion-condensation phenomenon in aqueous solution of sodium polystyrenesulfonate: a scaling theory approach

Abstract

Interactions between a polyion and its counterions in aqueous solutions of an anionic polyelectrolyte sodium polystyrenesulfonate in the presence of sodium chloride were investigated using electrical conductivity as the probe. The specific conductivity vs. polyelectrolyte concentration data were analyzed with an equation recently developed by us considering the scaling description for the conformation of a polyion chain. The influences of (a) the molecular weight and the concentration of the polyelectrolyte, (b) the added electrolyte concentration, and (c) the temperature on polyion–counterion interactions were investigated. The extent of counterion condensation was found to be greatly affected by the concentration and molecular weight of the polyelectrolyte, the concentration of the added electrolyte, and the temperature. The polyion equivalent conductivity in conjunction with the derived coefficient of friction between the monomer units and the solvent provided important information concerning the relative importance of the size and charge of the polyions. The overall results have been elucidated taking the medium dielectric constant, the hydration behaviour of the counterions, and the coiling behavior of the polyion chains into account. The present study provides new insight as to how the polyelectrolyte molecular weight influences the counterion condensation behaviour in a polyelectrolyte solution in the presence of an added electrolyte.