STRUCTURE AND DYNAMICS OF POLYMERIZABLE MICROEMULSIONS

The structure of polymerizable microemulsions containing styrene, dodecyltrimethylammonium bromide, and brine is investigated by small-angle neutron scattering (SANS) and quasielastic light scattering (QLS). SANS measurements suggest that these microemulsions consist of a unimodal population of swollen micelles that swell uniformly with the addition of styrene. The double exponential behavior of the autocorrelation function measured with QLS experiments is attributed to collective and self-diffusion modes. These modes appear in polydisperse systems at high volume fractions and are enhanced by repulsive interactions. The collective diffusion coefficient, which increases with added styrene and decreases with salt, depends on both hydrodynamic and thermodynamic interactions. The self-diffusion coefficient decreases monotonically with added styrene. Adding salt does not affect the size of the swollen micelles but does screen micelle interactions sufficiently that the contribution to the autocorrelation function from self-diffusion disappears. The experimental values characterizing hydrodynamic interactions agree well with a recently developed theory for small charged spheres.