Spontaneous emulsification of oil drops containing surfactants and medium-chain alcohols

Abstract

Spontaneous emulsification of mixtures of n-hexadecane, n-octanol, and the pure nonionic surfactant C₁₂E₆ brought into contact with water was observed using videomicroscopy. Relevant aspects of equilibrium phase behavior in this system were determined, and information on emulsion drop size and stability was obtained by turbidity measurements. It was found that small, uniform oil droplets and the most stable emulsions occurred when the entire original oil drop was converted to another phase — in this case a microemulsion — which subsequently became supersaturated in oil owing to diffusion of octanol into the aqueous phase. Spontaneous emulsification was also studied for mixtures of n-decane, n-heptanol, and tetradecyldimethylamine oxide contacting water. In this case, small droplets were formed when both the microemulsion and an intermediate lamellar liquid crystalline phase became supersaturated with oil.