Scattering from internal interfaces in microemulsion and sponge phases

Abstract

The scattering intensity due to thermal fluctuations of the amphiphile density in microemulsion and sponge phases is calculated for a Ginzburg-Landau model with two scalar order parameters. The amphiphile correlations are found to be strongly influenced by the oil-water correlation function in the former and the water-water correlation function in the latter. We take these correlations to oscillate with wave vector k. Not only does this reproduce the known 1/q dependence of the scattering intensity for the small wave vector q, it also gives rise at q=2k to an experimentally oberved peak. The calculated scattering intensities agree very well with experimental results over the whole range of wave vectors.