MICROEMULSIONS AND PHASE-BEHAVIOR OF SYSTEMS CONTAINING 2 OR TRI-CHAIN CATIONIC SURFACTANTS-WATER-ALKANES

Two series of di and tri-chain cationic surfactants were synthetized with the general formula of the di-chain surfactants as CnH2n+1 - (CmH2m+1) - N+ - (CH3)2Br- with n = 12 or 18, m = 3,5,6 or 8. The phase behavior of ternary mixtures containing water, oil and these cationic surfactants was investigated. For the dialkyldimethylammonium bromide surfactants the effect of the length of the variable chain on the curvature of the oil-water interface was examined. The general trends observed could be interpreted on the basis of geometrical constraints. In the case of triple-chain surfactants the lateral chains behave as attached co-surfactants when they were sufficient long. The overall effect of branching on the microemulsion formation was found difficult to predict since the lateral chains affect both the curvature and the flexibility of the interface.