Conductometric analysis of polyelectrolytes in solution

Abstract

Theoretical developments concerning ion association phenomena and their implications for conductivities of polyelectrolyte solutions are surveyed. Attention is focused on the characteristics of polyion/counterion association and conductivities of polyionic species. The existing literature on experimental studies of model systems is critically reviewed. Central issue is the analysis of counterion distribution, which may be quite typical in a certain range of polyionic charge densities. Simultaneously occurring intrinsic binding between polyion and counterion is taken into consideration. The rather extensive literature on conductometric protolytic titration of polyacids and polybases is reconsidered. Many conductometric titration curves for natural polyelectrolytes such as humic acids have originally been interpreted in terms of different types of functional groups. The present report shows that such interpretation is at least premature since the data are equally well explained by counterion association, as imposed by the polyionic charge densities involved. By utilizing the effects of counterion association (especially those of higher-valency ions), conductometry can be fruitfully applied in the quantitative analysis of charged groups on polyelectrolytes. © 1991 IUPAC