Transport phenomena in concentrated aqueous solutions of sodium–caesium polystyrene sulphonates

Abstract

The electrical conductivity, intradiffusion coefficients and ionic conductivities of sodium and caesium ions have been measured for polystyrene sulphonates in their heteroionic forms as a function of q, the number of water molecules per ionic group, at 298.15 K using a novel electrodiffusion technique. The trace diffusion coefficient and ionic conductivity of the chloride ion are also reported. The behaviour of the transport properties as a function of the water content and the ionic composition are analysed. The empirical relationships valid in homoionic sulphonic ion-exchangers hold in the heteroionic systems. Some anomalies are found in the sodium-rich region as a consequence of the formation of a lattice-like structure involving caesium ions. The counterion mobilities increase with the caesium content in the system, as found in ion-exchange membranes and electrolyte solutions. The ratio between electrical and diffusional mobilities of counterions follows the same trends observed in crosslinked ion-exchange systems and mixed electrolyte solutions, indicating that the polymer has a second-order effect.