Ostwald ripening in sodium dodecyl sulfate-stabilized decane-in-water emulsions

The kinetics of Ostwald ripening of decane-in-water emulsions stabilized by the anionic surfactant sodium dodecyl sulfate (SDS) was studied by means of photon correlation spectroscopy, The experimental rates of Ostwald ripening were compared with those predicted by Lifshitz-Slezov-Wagner (LSW) theory and were found to be higher at all surfactant concentrations. Below the critical micelle concentration (CMC), the experimentally determined rates were found to decrease with an increase in SDS concentration, in agreement with the theory. Above the CMC, the ripening rates were found to increase with an increase in micellar concentration, The increase in the rates is attributed to the enhancement of mass transfer between droplets by micelles, which is not accounted for by LSW theory. The volume fraction of the dispersed phase was found not to affect the rates in the low concentration range (0-0.002) used in this study. (C) 1996 Academic Press, Inc.