Phase behavior, small-angle neutron scattering and rheology of ternary nonionic surfactant-oil-water systems: a comparison of oils.

The phase behavior of the nonionic surfactant Triton X-100 (polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether) was studied in two three-component systems: Triton-water-p-xylene and Triton-water-trichloroethylene. It was found that the aromatic solvent was able to produce monophasic soft matter systems at a significantly greater range of compositions. The structural characteristics of the phases generated were analyzed by small-angle neutron scattering, showing evidence for microemulsion, lamellar, and reverse-microemulsion phases. In addition, for the Triton-water-p-xylene system, an L3 "sponge" phase was found in a water-rich region of the phase diagram and the properties of this were examined using rheological measurements. The differences in phase behavior are discussed in light of the solvation properties of the surfactant in the different solvents studied. Most notably, xylene appears to favor phases with low-curvature interfaces, suggesting preferential solvation of the central phenyl group of Triton.