Studies on macro- and microstructures of highly concentrated water-in-oil emulsions (gel emulsions)

Macro- and microstructures of highly concentrated water-in-oil (W/O) emulsions were investigated in a water (or brine)/tetraethylene glycol dodecyl ether/decane system by means of phase studies, VEM (video-enhanced microscopy), and NMR self-diffusion coefficient measurements. The W/O emulsion consists of a small portion of oil or surfactant phase (continuous medium) and a large amount of water phase containing monomeric surfactant. The effects of temperature and NaCl on the stability were observed by VEM. In the water-rich corner of the main miscibility gap of the ternary phase diagram, the two-phase system can be classified into regons of stable emulsions and regions of extremely unstable emulsions. The NMR self-diffusion coefficient measurements show that the continuous phase is a reverse micellar solution in the stable-emulsion region but it is a bicontinuous microemulsion in the extremely unstable-emulsion region.