Dynamic properties and structure of salt-free polystyrene sulphonate solutions

Abstract

Dilute solution properties of polystyrene sulphonate polyelectrolytes of different molecular weight and with different counterions have been studied conductometrically and viscosimetrically. In the concentration range encompassing the critical overlap concentration for individual molecules marked changes in the solution properties occur. The effect is molecular-weight-dependent and most pronounced in solutions of polystyrene sulphonic acid. For low-molecular-weight samples the equivalent conductivity and reduced viscosity of the solutions increase steadily on dilution, whereas for high molecular-weight samples a rapid decrease of these quantities is observed in very dilute solutions. This indicates that the polyelectrolyte molecules assume more compact conformations when the molecular domains become separated. The effect is attributed to the presence of attractive interactions, possibly of hydrophobic origin, between elements of the polyelectrolyte chain.