THE FORMATION AND AGING RATES OF OIL-IN-WATER MINIEMULSIONS

The rates of ageing of emulsions formed by the dilution of oil-in-water (O/W) microemulsions (SDS/dodecane/pentanol/water) were investigated as a function of various parameters, namely volume fraction, surfactant concentration, and salt concentration. It was found that the ageing process could be explained in terms of Ostwald ripening, with experimental rates showing some agreement with those calculated using the Lifshitz, Slezov and Wagner theory. It was also found that the presence of micelles had relatively little effect upon the rate of ripening and this was tentatively explained in terms of micellar breakdown. It was concluded that the dilution of O/W microemulsions offered a possible route for the preparation of miniemulsions, i.e. emulsions with radii of the order of 100-200 nm.