Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract In this paper we bring together some recent results concerning the stability and properties of O/W microemulsion droplets in a ternary system composed of water, decane and the nonionic surfactant pentaethylene glycol dodecylether (C12E5). Stable microemulsion droplets can be prepared when the spontaneous curvature has a finite but not too low value. Near the limit of maximum oil solubilisation the droplets adopt a spherical shape with low polydispersity. Experimental results obtained from low shear viscosity, collective and long time self-diffusion and static light scattering show that the spherical droplets interact to a very good approximation as hard spheres over a large range of volume fractions. A supersaturated microemulsion can be prepared by a rapid temperature quench (drop) into the two-phase area where a smaller droplet size coexists with excess oil. In the two-phase area, we can distinguish a region near the microemulsion phase boundary where the droplets are metastable, from a region further away from the boundary where the droplets are unstable and the oil-phase nucleates instantaneously. Treating the initial phase separation as a homogeneous nucleation it is possible to calculate an activation energy within the curvature energy approach.
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