Electrical conductivity properties of poly[(maleic acid)-co-(vinyl pyrrolidone)] salts in aqueous solutions

The interaction of alkaline ions with an anionic dicarboxylic polyelectrolyte is studied by means of electrical conductivity measurements. The results show that lithium, sodium and potassium counter-ions interact in a very different way with this polyelectrolyte. The Kohlrausch plots bend downwards in the high-dilution zone. The limiting equivalent conductivities of these polymers were then determined according to Vink's method by a polynomial adjustment of specific conductivity data. Whereas the dissociation order follows the sequence Li+ > Na+ > K+, the trend in equivalent conductivity follows the reverse order, and apparently is mainly determined by the equivalent conductivity of the counter-ions. The interaction parameter f was determined using the Manning theory for the limiting equivalent conductivity of the polyion species. From the values of the latter parameters, the average distance between charges agrees well with that calculated from simple geometrical calculations for a mesomeric configuration. An alternative method was used to obtain the relative interaction parameter f* as a function of polymer concentration. The results can be explained in terms of the hydration parameters and the limiting equivalent conductivities of the counter-ions. (C) 2001 Society of Chemical Industry.