Thermodynamic properties of concentrated heteroionic polyelectrolyte solutions

Abstract

The water sorption isotherms of concentrated sodium–caesium polystyrene sulphonate solutions have been measured as a function of the ionic composition at 298.15 K. Also the densities of the solid-like solutions are reported at various water contents. The systems obey the B.E.T. isotherm only over a limited range of concentration, but empirical equations have been found which describe the behaviour of the linear and crosslinked ion-exchangers over the concentration range of practical interest. The heteroionic systems studied here are far from ideal behaviour; anomalies are found in the sodium-rich region, probably caused by a lattice-like structure involving caesium ions.