EFFECT OF COUNTERION SUBSTITUTION ON THE TRANSPORT PROPERTIES OF POLYELECTROLYTE SOLUTIONS

The effects of counter‐ion substitution in aqueous polyelectrolyte solutions (chondroitin sulfate) on the two main transport phenomena of the ionic species, self‐diffusion and electrical mobility, were studied experimentally by tracer methods and dynamic light scattering. The data were analyzed with respect to counter‐ion condensation and stoichiometric substitution of low‐ionic counterions by high‐ionic charge ones and compared to Manning's theory. Substitution effects on the apparent charge of the macro‐ion were derived from the transport data using an extended Nernst‐Einstein relationship and discussed in the light of the condensation effect in polyelectrolyte solutions. The effective charge of the polyion (i.e., its residual charge after condensation of counter‐ions) and the charge difference between the substituting counter‐ions appear determinant in the mechanism of substitution. Copyright © 1979 John Wiley & Sons, Inc.