Sodium-23 quadrupole splittings in lyotropic liquid crystals. Relationship to electrical double layer theory and estimates of double layer dimensions

Abstract

It is proposed that the magnitudes of n.m.r. quadrupole splittings of ions in lyotropic liquid crystals are related to the fractional concentration of the ions in the bound water at the lipid/water interface. Ions in the remaining water have zero splittings. Sodium-23 splittings are reported for cationic and anionic amphiphile systems at different salt concentrations and strongly support the proposed explanation. In favourable cases it is possible to obtain measurements of the double layer thickness. It was not possible to observe any displacement of sodium ions by magnesium or lanthanum ions in the concentration ranges studied.