Percolation in nonionic water-in-oil-microemulsion systems: A small angle neutron scattering study

Nonionic water-in-oil (w/o)-microemulsions of the type water/c-hexane, n-hexane/Igepal were examined by SANS in both shell and core contrast. Variation of the water to surfactant ratio W-0 in the droplet regime yields a linear relation between W-0 and the droplet water core radius and R/nm = 0.19 W-0 + 0.70. Small angle neutron scattering (SANS) data for W-0 = 10 samples show that droplet aggregation occurs with a fractal dimension of D less than or equal to 1.3 as a percolation-like transition is crossed by decreasing temperature. Data analysis and model calculations, done in both q and r space, are consistent with the formation of linear aggregates of discrete spherical droplets.