Analysis of water self-diffusion in polycrystalline lamellar systems by pulsed field gradient nuclear magnetic resonance experiments

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Abstract
A study of the water self‐diffusion in polycrystalline lamellar systems, by pulsed field gradient spin‐echo (PFG‐SE) nuclear magnetic resonance(NMR) experiments, is reported here. Our analysis confirmed the validity of previous equations for bidimensional water self‐diffusion in lamellar lyomesophases and clarified their applicability limits. Depending on the diffusion experimental time range, two different procedures can be built up; for wide amplitude windows, the experimental diffusion coefficients are correlated to the fraction of bound water, whereas for short times it has been possible to point out the ‘‘obstruction factor’’ to diffusion. Experimental support for the theoretical findings was inferred by investigation of the lamellar mesophase of the binary system water/sodium‐bis‐2‐ethylhexyl sulfosuccinate (AOT). It confirmed the existence of some defects in the lamellae at water concentration higher than 70 wt. %.