Structural changes induced in the surfactant system C12E4/benzyl alcohol/water by the admixture of the cationic surfactant cetylpyridinium chloride

The influence of the addition of the cationic surfactant cetylpyridinium ch loride (CPyCl) on the structure of the different phases of the ternary surf actant system C12E4/benzyl alcohol/water in the dilute region has been stud ied by means of small angle neutron scattering (SANS) and freeze-fracture m icroscopy (FF-TEM). In the ternary system various different subregions of t he L-alpha-phase were identified as a function of the concentration of the cosurfactant, benzyl alcohol. Addition of small amounts of CPyCl suppresses these different L-alpha-phases in favor of the one composed of multilamell ar vesicles. Addition of somewhat larger amounts (up to 2 mol% relative to the total surfactant concentration) destabilizes the formation of bilayer s tructures completely and leads to the formation of micellar solutions. This demonstrates that in this surfactant system the incorporation of very smal l amounts of cationic surfactant has a pronounced and systematic fluence on its phase behavior and its structures. (C) 2001 Academic Press.