Ionic charge effects on the transport processes in polyelectrolyte solutions

Abstract

A comprehensive treatment of transport processes in polyelectrolyte solutions in the presence of simple salt is given. The treatment is based on the frictional formalism of nonequilibrium thermodynamics and is mainly concerned with isothermal diffusion and sedimentation in the ultracentrifuge. It is shown that the flows of the polyion and the counterions, which are coupled in the absence of salt, become fully decoupled at high concentrations of simple salt. In sedimentation the observed sedimentation constant of the polyelectrolyte is a simple average of the sedimentation constants corresponding to these limiting processes. In diffusion the situation is more complex, and no simple average of the diffusion coefficient exists. Implications of the theory on the interpretation of experimental results are discussed.