Observing diffusive exchange between surfactant and aqueous domains in detergents.
Nuclear magnetic resonance (NMR) two-dimensional relaxation correlation experiments have been used to study an industrially relevant formulation of surfactant multilamellar vesicles (MLVs) in an aqueous solution. By correlating transverse T2 relaxation measurements before and after a storage interval, diffusive exchange of water molecules between domains can be observed. Two average exchange times of 0.04 and 0.83 s were determined by solving the one-dimensional Fredholm integral form of a model for region-to-region exchange. Diffusion coefficients for the restricted and free water fractions within the mixture determined via chemically selective pulsed field gradient (PFG) NMR measurements allowed exchange distances of 6.2 and 81 microm to be determined from the exchange times. These exchange distances are associated with the average MLV diameter and speculatively with the size of MLV clusters, respectively.
Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK.
Jonathan D
JD
Griffith
Jonathan
J
Mitchell
Andrew E
AE
Bayly
Michael L
ML
Johns
D003902:Detergents / Q000737:chemistry*; D004058:Diffusion; D008956:Models, Chemical; D016062:Porosity; D011336:Probability; D015203:Reproducibility of Results; D014867:Water / Q000737:chemistry*
D003902:Detergents; D014867:Water