SANS studies of the microstructure of a three-componnent microemulsion

Small-angle neutron scattering measurements have been performed on a three-component microemulsion system consisting of water, hexane and didodecyl-dimethylammonium bromide. For a water-to-surfactant weight ratio of 0.95 and less than 5 wt% surfactant, these measurements are best fit by a model with a Gaussian size distribution of spherical water droplets in hexane. The average water core radius is determined to be about 2.9 nm. On addition of water while the same water-to-surfactant ratio is maintained, there is some evidence that the basic unit of the microstructure remains a sphere with the same radius. The interaction between the spheres is found to be attractive, and the spheres may be connected for volume fractions of water larger than 5%.