Ion binding to polyelectrolytes as described by the Poisson–Boltzmann equation. Comparison with 23Na nuclear magnetic resonance relaxation experiments

Abstract

Experimental data on ²³Na n.m.r. transverse relaxation rates in aqueous solutions of the sodium salts of poly(acrylic acid) and chondroitin-4-sulphate at different polymer concentrations are presented, as well as experimental data on ²³Na n.m.r. longitudinal and transverse relaxation rates for poly(acrylic acid) at various degrees of neutralization. The data are compared with a theory based on the Poisson–Boltzmann equation. The theory is also compared with literature data on ²³Na n.m.r. linewidths in Na⁺–DNA solutions as a function of the concentration of salt containing monovalent or divalent counter-ions. The comparison between the theory and experiments reveals that the Poisson–Boltzmann theory in all cases accounts satisfactorily for the experimental results.