Studies of micellar solutions of cationic double-tailed surfactants and investigations of bicontinuous microemulsions

The micellar properties of three double-tailed cationic surfactants were studied. All three surfactants were found to be insoluble in water. Two of the compounds, diesters, were soluble in n-hexane and isooctane; however, the reverse micelles formed in these solutions did not solubilize a measurable amount of water. The third compound, a diamide, was insoluble in n-hexane and isooctane. Small-angle neutron scattering was used to determine the size and shape of the reverse micelles formed in isooctane by the diesters. The aggregates were found to be approximately spherical with radii of 12-13 A.

Phase studies were carried out on the mixed surfactant system involving SDS and AOT. In a molar ratio of 25% SDS and75% AOT a one phase microemulsion region was determined for the system using n-octane and water. Conductivity measurements indicated that the system was water-continuous.

Attempts to use gelatinization to determine the microstructure of DDAB/n-octane/water microemulsions are also reported. These systems are believed to undergo a phase transition from water-continuous to water-discontinuous as the water content increases. The gelatinization technique was not successful due to the inability of the system to incorporate the gelatin.