Control over Microemulsions with Solvent Blends

The effect of solvent mixtures on the phase behavior of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) stabilized water-in-oil microemulsions has been studied by using heptane/dodecane, decane/dodecane, octane/dodecane, and nonane/undecane blends. Small-angle neutron scattering was employed to explore the effect of changing the solvent composition on the microemulsion properties, especially near the cloud point (T(cloud)) and the liquid-liquid critical separation (T(crit)). It is shown that droplet interactions can be strongly influenced by changing the solvent blend compostion, which has implications for the locations of observed phase boundaries. Of particular interest is the use of carefully selected solvent blends, which have the effect of lowering T(crit) by up to 6 degrees C from the value found in pure decane.