17 Pages

Osmotic pressure and viscoelastic shear moduli of concentrated emulsions

An emulsion is an immiscible mixture of two fluids, one of which is dispersed in the continuous phase of the other, typically made by rupturing droplets down to colloidal sizes through mixing. To inhibit recombination, or coalescence, a surfactant which concentrates at the interfaces must be added to create a short-ranged interfacial repulsion between the droplets [ 1,2]. For an appropriate surfactant, a quantity much less than the mass of the liquids is often sufficient to make this interfacial repulsion strong enough to render the emul­ sion kinetically stable against coalescence and demixing for many years. This kinetic stability differentiates emulsions from thermodynamically stable microemulsions which form spontaneously without mixing when the proper proportions of certain fluids and surfactants are placed in contact.