SHORT-RANGE INTERACTION IN A POLYELECTROLYTE SOLUTION CONTAINING A MIXTURE OF MONO- AND DIVALENT COUNTERIONS
D. Dolar and M. Bešter Rogač Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000-Ljubljana, Aškerčeva 5, Slovenia
The osmotic coefficient and the excess free energy have been calculated for a polyelectrolyte solution with mixtures of mono and divalent counterions. The results have been obtained by applying the cylindrical cell model in the Poisson-Boltzmann approximation. The short-range interaction between polyion and counterions, described by a square-well potential, has also been taken into account. The results of osmotic coefficient are presented as functions of the equivalent fraction of monovalent counterions for different values of ionic radii, depth of the potential well, and concentration.