INTERFACIAL-TENSION OF IONIC MICROEMULSIONS

Interfacial tension measurements are reported on the system didodecyldimethylammonium bromide/water/alkane against alkane for a range of alkanes and surfactant/water ratios. The data span values from low (0.15 dyn/cm) to very low (5 × 10-3 dyn/cm). Physical properties of these microemulsions enable microstructure to be sufficiently well established to correlate interfacial tension with structure. Long-range and extremely strong van der Waals forces peculiar to cylindrical geometries have long been known to exist theoretically. These forces operative for high dielectric and/or conducting rods (water) interacting across a low dielectric constant medium (oil) appear necessary to account for the observations. © 1987 American Chemical Society.