Spontaneous emulsification produced by chemical reactions

Spontaneous emulsification of small oil droplets was produced in three different systems by chemical reactions which converted lipophilic surfactants initially dissolved in the oil phase to hydrophilic surfactants. The resulting reversal of spontaneous curvature from a water-in-oil to an oil-in-water configuration reduced the solubilization capacity for oil to such an extent that supersaturation occurred, leading to nucleation of oil droplets. In one case a dilute solution of phenylboronic acid in water diffused into an oil phase containing a monoglyceride. The reaction converted the monoglyceride to an anionic surfactant. In another case a dilute aqueous solution of the sodium salt of EDTA diffused into an oil phase containing a calcium sulfonate surfactant. The EDTA complexed calcium ions, releasing sodium ions which formed the more hydrophilic sodium salt of the sulfonate. Finally, an enzyme was used to split a double-chain phospholipid into a lysolecithin and a fatty acid. (C) 2001 Academic Press.