Droplet interfacial structure studied by SANS contrast variation

Details of structure and composition at interfaces may be obtained by Small Angle Neutron Scattering (SANS) contrast variation. At the curved oil/surf actant/water interfaces of microemulsion droplets useful results may be obt ained by simultaneous fits of core-shell models to SANS data measured at di fferent scattering contrasts. Results for small ethyl octanoate/dimethyldod ecylamineoxide/water droplets, where the oil core penetrates the surfactant layer, will illustrate this method. For block-copolymer micelles with deut erated poly( lactic acid) core, the composition profiles of thicker poly( e thylene glycol) shells were obtained using a model with a vertical step and two diffuse shells. One of the three water contrasts used was close to the "mean contrast" match point for the whole micelle, as opposed to "shell" c ontrast, providing a peak in the form factor very sensitive to the model us ed.