Mutual and Intradiffusion Coefficients for the Binary System n-Decyl Dimethyl Phosphine Oxide + Water at 25 °C

Abstract

Diffusion coefficients for the binary system n-decyl dimethyl phosphine oxide + water have been studied at 25 °C, with the aim to quantitatively describe the surfactant micellization process in aqueous medium. Accurate mutual diffusion coefficients have been measured by the Taylor dispersion technique. Intradiffusion coefficients of both components have been measured by the pulsed gradient spin echo (PGSE)-FT NMR technique. The data have been compared and interpreted in the framework of the equilibrium model of surfactant self-aggregation. Interpolation of the mutual diffusion coefficients has allowed us to estimate reliable values of the average number of surfactant molecules involved in the formation of a micellar aggregate and the constant of the equilibrium between these aggregates and surfactant unimers. Interpolation of water intradiffusion coefficients has allowed us to estimate the number of water molecules involved in the hydration of surfactants in unimeric and micellized form.

Microstructural characterization of lysophosphatidylcholine micellar aggregates: The structural basis for their use as biomembrane mimics

“…(8) to the premicellar D W data allows estimating h m . The values, collected in Table 2, are of the same order of those obtained for other surfactants [17,34]. Intradiffusion coefficients allow to estimate the total number of water molecules whose motion is slowered down by the interaction with a solute.…”

On the Segregative Tendency of Ethoxylated Surfactants in Nonionic Mixed Micelles

“…Briefly, both the D C 6 DMPO and D W trends allow evaluating the C 6 DMPO critical micellar concentration, cmc C 6 DMPO ; from the D C 6 DMPO M values, by using the Stokes−Einstein equation, the hydrodynamic size of the aggregates, R app , can be estimated. Analysis of the D W data, according to a two-site model, leads to the number of water molecules hydrating each surfactant in both monomeric and micellized form, h m and h M , respectively . Finally, the obtained R app and h M values allow estimating the aggregation number of C 6 DMPO micelles, N .…”

“…Analysis of the D W data, according to a two-site model, leads to the number of water molecules hydrating each surfactant in both monomeric and micellized form, h m and h M , respectively. 27 Finally, the obtained R app and h M values allow estimating the aggregation number of C 6 DMPO micelles, N.…”