Modelling fast mode dielectric relaxation of counterions in aqueous solutions of ionene bromides and fluorides

Abstract

The parameters derived from previously published dielec. spectra of aq. solns. of aliph. 3,3-, 4,5-, 6,6-, and 6,9-ionene bromides and fluorides were analyzed within the existing models for the fast counterion-relaxation process. By fitting the Poisson-Boltzmann results to the exptl. data for the osmotic coeffs. of the ionenes in question, we were able to est. the self-diffusion coeffs. of counterions. The coeffs. were then used to calc. the correlation lengths as proposed by the Ito model. The corresponding correlation lengths obtained by the Mandel-Manning model were of similar magnitude. The obsd. trends in correlation lengths were consistent with the model-independent values derived from the exptl. relaxation times. Combination of the dielec. data and Poisson-Boltzmann model anal. yields the conclusion that the fluoride counterions prefer longitudinal, whereas the bromide counterions favor transverse, fluctuation with respect to the polyelectrolyte backbone.