SPONTANEOUS FORMATION OF A WATER-CONTINUOUS EMULSION FROM A W/O MICROEMULSION

A new mechanism for spontaneous emulsification is proposed which involves inversion of a highly viscous W/O microemulsion, formed from the methyl ester of partially hydrogenated rosin containing 5 wt % of the potassium salt of partially hydrogenated rosin acid and small amounts of water, by a quiescent adjacent water phase. Inversion leads to the formation of stable, rather homogeneous O/W emulsions containing oil droplets as small as 150 nm. The proposed mechanism involves osmotically driven swelling of inverted micelles in the W/O microemulsion which remain fixed in a small volume element because of the high viscosity of the oil phase. The inverted micelles interconnect as they grow and eventually invert. They are then driven apart by electrostatic repulsion and move into the adjacent water phase. It was found that 2 M sucrose and 1 N solutions of 1:1 electrolytes in the quiescent water phase completely inhibit emulsification. This process contains a number of features which are not accounted for by the spontaneous emulsification mechanisms previously described in the literature.