Water/oil microemulsions from binary ionic-nonionic surfactants

The addition of a second surfactant to an otherwise thermodynamically stable microemulsion causes interfacial and bulk effects: the combination of AOT and C(12)E(5) supports the formation of planar interfaces (considering the molecular geometries of the surfactants) which induces a sphere to oblate ellipsoid (approximate to disk) transition ensuing a lamellar liquid crystalline phase. Heats of adsorption of C(12)E(5) (adsorbed on an H2O/AOT/i-C8H18 interface) corroborate the existence of two different interfacial states. The phase transition was inferred from combining conductometric and electro-optic Kerr effect studies.