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.