Phase Behavior and Microstructure of Nonaqueous Microemulsions. 2

The microstructure of nonaqueous microemulsions formed with propylene glycol, glycerol, three different alkanes, and pentaethylene glycol mono-n-dodecyl ether (C{sub 12}E{sub 6}) is probed with NMR self-diffusion measurements and small angle neutron scattering (SANS). At low oil concentrations, both NMR self-diffusion and SANS results can be modeled in terms of a microstructure of ellipsoidal oil-rich droplets with only excluded volume interactions. These droplet structures percolate to an oil-continuous structure as the volume fraction of oil in the microemulsions increases. Percolation thresholds measured as a function of alkane chain length are interpreted in terms of the phase behavior of the microemulsion and the strength of droplet interactions. 41 refs., 6 figs., 3 tabs.