Studies of electrical transport processes in polyelectrolyte solutions

Abstract

Electrical transport parameters for a number of different polyelectrolytes in salt-free solutions have been determined by electric conductivity and transference measurements. To determine the transport numbers a new modified Hittorf method was used. Measurements were carried out with carboxymethylated cellulosic polyelectrolytes, poly(acrylates) and poly-(styrene sulphonates), with various univalent counterions. In measurements with different alkali-metal counterions small differences in ion binding existed in the carboxylic polyelectrolytes, but no differences could be detected in the poly(styrene sulphonates). Quaternary alkylammonium counterions were bound to a lesser extent than the alkali-metal ions in the carboxylic polyelectrolytes but more strongly in the poly(styrene sulphonates). This indicates the existence of hydrophobic interactions in the latter system. The equivalent conductivity of the polyion did in general depend on the counterion species, and decreased when the equivalent conductivity of the latter decreased. This is due to the contribution of the bound counterions to the hydrodynamic friction of the polyion, which increases with the size of the counterion.