OSTWALD RIPENING OF CONCENTRATED ALKANE EMULSIONS - A PRELIMINARY-REPORT

Fiber optic dynamic light scattering (FODLS) was used to study the kin etics of aging processes in emulsions of n-alkanes stabilized by a sur factant. The method is particularly useful for this purpose because it permits measurements in concentrated emulsions. Complications that ma y occur in traditional DLS due to the extreme dilution, such as solubi lization of the particles in the medium, can be easily avoided in this way. The experimental results show that the main aging process is Ost wald ripening. The results are in agreement with theoretical predictio ns based on the Lifshitz-Slyozov-Wagner (LSW) theory as far as it conc erns the relation between the molecular solubility of the n-alkanes (i n the aqueous phase) and the Ostwald ripening rate. This illustrates t hat the main rate-determining factor is the molecular diffusion of the alkane molecules through the continuous (aqueous) phase. The Ostwald ripening rate is affected by the concentration of surfactant but in al l situations is higher than expected from LSW theory.