Ionic surfactant influence over the phase behaviour of a nonionic surfactant based system

Addition of a small amount of ionic surfactant, as SDS, to a non ionic surfactant based system stabilizes the water rich region, thus it can improve the water-decan co-solubilization. The system becoming more stable with respect to temperature, the Phase Inversion Temperature is shifted towards higher temperatures. The structural study of the system : water/(C12EO6 + 1,5 % SDS)/decan shows that the crystal phases are lamellar, cubic and direct hexagonal structures at 30 degrees C. Their structural parameters are determined by small angle X-ray scattering. The study of different regions allows the description of the evolution of the surfactant chains conformation.