Interfacial Compositions and Phase Structures in Mixed Surfactant Microemulsions

• DOI: 10.1021/la990060m
• Publication Date: 2002-07-26T05:42:57Z
• Authors: Ali Bumajdad; Julian Eastoe; Peter Griffiths; David C. Steytler; Richard K. Heenan; Jian R. Lu; Peter Timmins
• Keywords: Microemulsion; Sodium dodecyl sulfate

Well-defined mixtures of didodecyldimethylammonium bromide (DDAB), with either n-dodecyltrimethylammonium (DTAB), sodium n-dodecyl sulfate (SDS), or pentaethylene glycol monododecyl ether (C12E5), have been used to stabilize water-in-heptane microemulsions. Using DTAB C12E5 DDAB causes a synergistic effect, and the water solubilization capacity microemulsion is increased. However, SDS there destabilization, indicating surfactant antagonism. Structure dynamics in these systems studied as function type composition using small-angle neutron scattering (SANS) pulsed-field gradient NMR (PFG-NMR). Compositions mixed films at oil−water interfaces also measured, by blending deuterated proteated C12E5, carrying out contrast variation SANS experiments. For both DDAB/DTAB DDAB/C12E5 mixtures, all added was strongly adsorbed no evidence for any significant partitioning into solvent phases. These results show that changes phase behavior properties are direct consequence preferred film curvature, which may be varied mixing interface.