MIXED SURFACTANT SYSTEMS OF SODIUM PERFLUOROOCTANOATE WITH NONIONIC, ZWITTERIONIC, AND CATIONIC HYDROCARBON SURFACTANTS

Mixed surfactant systems of sodium perfluorooctanoate (SPFO) with N-triethoxylated heptanylamide (HEA8-3), with 3-(decyldimethylammonino)-1-propanesulfonate (DEDIAP), and with octyltrimethylammonium bromide (OCTAB) have been studied by the use of surface tension and F-19 and H-1 NMR. The results show that only one type of mixed micelle is formed for the mixed system of SPFO/HEA8-3 as well as the system of SPFO/DEDIAP. Pseudo phase diagrams for both mixed systems are calculated from the dependence of the critical micelle concentrations (cmc's) on the mole fraction of the fluorocarbon component, and they show large negative deviation from ideal behavior. For the mixed systems of SPFO/OCTAB, the cmc's and surface tensions are reduced tremendously upon mixing, and the NMR studies combined with centrifugation results suggest the mixed surfactants coacervate to form large aggregates.