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An NMR study of translational diffusion and structural anisotropy in magnetically alignable nonionic surfactant mesophases

TitleAn NMR study of translational diffusion and structural anisotropy in magnetically alignable nonionic surfactant mesophases
Publication TypeJournal Article
Year of Publication2005
AuthorsYethiraj, A, Capitani, D, Burlinson, NE, Burnell, EE
JournalLangmuir
Volume21
Pagination3311-3321
Date PublishedApr
Type of ArticleArticle
ISBN Number0743-7463
KeywordsC12E6/D2O SYSTEM, C16EO6/WATER SYSTEM, CUBIC PHASES, LAMELLAR PHASE, LYOTROPIC LIQUID-CRYSTAL, MICELLAR-SOLUTIONS, OBSTRUCTION, RESONANCE, SELF-DIFFUSION, WATER MESOPHASES
Abstract

The diffusion of both water and surfactant components in aqueous solutions of the nonionic surfactant "C12E6"-which includes hexagonal, cubic, lamellar, and micellar mesophases-has been studied by pulsed-field-gradient NMR. Diffusion coefficients were measured in unaligned samples in all of these phases. They were also obtained in the hexagonal and lamellar phases in oriented monodomain samples that were aligned by slow cooling from the micellar phase in an 11.7 T magnet. Measured water and soap diffusion coefficients in the NMR-isotropic cubic and (high-water-content) micellar phases as well as diffusion anisotropy measurements in the magnetically aligned hexagonal phase were quantitatively consistent with the constituent structures of these phases being identical surfactant cylinders, with only the fraction of surface-associated water varying with the water-soap molar ratio. The values of the water and soap diffusion coefficients in the oriented lamellar phase suggest an increase in defects and obstructions to soap diffusion as a function of increasing water content, while those in the low-water-content micellar phase rule out the presence of inverse micelles.

URL<Go to ISI>://000228218700019