Proton magic-angle spinning-NMR investigation of surfactant aqueous suspensions.

In this Note we present the advantages of 1H magic-angle spinning nuclear magnetic resonance (MAS-NMR) for the investigation of surfactant suspensions via transverse relaxation rate (R2) measurements. 1H-relaxation rates can be determined by the classical CPMG method from high-resolution spectra obtained either under conditions of liquid-state NMR for monomers and small spherical micelles or by using MAS-NMR for larger aggregates. For a mixture of alkyl dioxyethylene sulfate and alkylbetaine (80:20, w/w), up to a percentage of surfactant in water of 20%, we found that R2 increased, in accordance with an increased micellar size and very likely the formation of an HI phase.