Surfactant diffusion

Abstract

Data for surfactant diffusion are reported for sodium dodecyl sulfate at 25°C and tetradecyltrimethylammonium bromide at 25, 90, and 135°C, as measured by Taylor tube dispersion. These data are analyzed in terms of two limiting forms of theory, one appropriate to "slow" reaction rates, the other to "fast" rates. It is shown that the usual extrapolation to the critical micelle concentration to infer intrinsic diffusion constants is not permissible. The data are explicable if transport occurs by a process wherein ionic micelles disassociate, diffuse as monomers, and reassemble into micelles. This is directly contrary to current ideas on diffusion of surfactants. Show more