Evaluation of the Counterion Condensation Theory from the Metal Ion Distributions Obtained by Ultrafiltration of a System Poly(sodium 4-styrenesulfonate)/Cd2+/Na+

The metal ion distributions of a solution of poly(sodium 4-styrenesulfonate) in the presence of Cd 2+ and Na + ions are obtained by ultrafiltration. The results are used to evaluate the Manning's two-variable counterion condensation theory concerned with long-range interactions. The original theory results are insufficient to explain the metal ion distributions obtained, and short-range interactions have to be included. We also propose the inclusion of the influence of the polymer conformations in the theory.