DYNAMIC BEHAVIOR OF ALCOHOL DROPS IN DILUTE-SOLUTIONS OF AN AMINE OXIDE SURFACTANT

Dynamic contacting experiments were conducted in which drops of short- chain alcohols were injected into dilute aqueous solutions of tetradec yldimethylamine oxide (C(14)DMAO) and the resulting behavior was obser ved using videomicroscopy. At neutral values of pH the L(3) (sponge) a nd the L(alpha) (lamellar) phases formed successively as intermediate phases during the experiments. Most of the observed behavior could be explained in terms of the equilibrium phase diagrams and a quasi-stead y-state diffusion model which is a generalized version of one develope d previously, Although the drops shrank in the early part of the exper iments owing to diffusion of alcohol into the aqueous phase, they bega n to grow once the L(3) phase formed because incorporation of surfacta nt and water exceeded alcohol losses, Even though no convection was ob served, a striking rapid expansion occurred when equilibrium condition s at the interface between the L(3) phase and the aqueous solution dic tated that the former incorporate water at a rate much faster than the rates at which surfactant diffused into or alcohol diffused out of a drop, Indeed, the drops seemed to explode as their surfaces became irr egular, apparently due to formation of a highly dilute lamellar phase which grew extremely rapidly as myelinic figures, At low pH where the surfactant was cationic, only a lamellar intermediate phase was seen, evidently because the charged bilayers were too rigid to form the L(3) phase. (C) 1995 Academic Press, Inc.