Scattering by polydisperse hard sticky spheres and the Porod-Auvray law for mixtures of large and small particles

The structure of fluorinated gel-emulsions made of water globules dispersed into an (oil) fluorocarbon phase has been investigated by SANS , the water volume fraction being as large as 98 %. The oil continuous phase is a water swollen micellar phase, with a volume fraction of the micelles in the range of 10 - 40 %. The determination of the specific area of the water globules was performed by using the Porod-Auvray law. The validity of the approximation where the heterogeneous micellar phase is considered as being a homogeneous continuum is discussed by comparing to calculations for polydisperse hard-sticky spheres within the P.Y. approximation.