Mixed concentrated water/oil emulsions (fluorinated/hydrogenated):: Formulation, properties, and structural studies

Highly concentrated water-in-oil emulsions consisting of mixtures of five compounds (a fluorinated surfactant, a hydrogenated surfactant, a fluorocarbon, a hydrocarbon, and water) have been prepared. The formulation and properties of these peculiar emulsions obtained from compounds with antagonistic behaviors have been examined. These mixed emulsions are stable and present macroscopic properties comparable to those of concentrated emulsions prepared with purely hydrogenated compounds. The study of the phase behavior shows that the mixed emulsions are triphasic systems constituted by two kinds of mixed microemulsions coexisting with an aqueous phase. The composition of these microemulsions has been determined by quantitative NMR studies. The five compounds are present in both microemulsions, but one of them is rich in fluorinated compounds and the other in hydrogenated ones. Small-angle neutron scattering experiments allowed us to propose a structure for these mixed emulsions. The bulk of the continuous medium is made of a mixed microemulsion rich in hydrogenated compounds, whereas the mixed microemulsion rich in fluorinated compounds is dispersed inside the continuous medium.