Ion condensation model and nuclear magnetic resonance studies of counterion binding in lyotropic liquid crystals

Abstract

It is suggested that the ion condensation hypothesis, previously used for polyelectrolyte solutions, also describes the ion binding in lyotropic liquid crystals formed in mixtures of amphiphiles and water. Counterion n.m.r. quadrupole splittings of these systems are shown to be appropriate for testing the ion condensation model. Data on ²³Na⁺ quadrupole splittings are found to be in good agreement with the ion condensation approach. In particular, the effects of varying the water content, the concentration of added salt and the temperature are discussed. A previous conclusion concerning the thickness of the electrical double layer in lamellar liquid crystals is shown to be incorrect. The magnitude of the quadrupole splitting is estimated by means of a solution to the Poisson–Boltzmann equation obtained previously. Comparison with experimental data suggests that the field gradients at the nucleus are mainly determined by local effects.