Comparative Phase Behavior About the L2 Phase of Ternary and Quaternary Systems of Triton X-100 and Its Separated p-tert-OPEn (n = 5, 7, and 9) Components in Cyclohexane

Abstract

The nonionic surfactant Triton X-100 (TX-100) is separated by preparative column chromatography into its poly(oxyethylene tert-octylphenyl ether) (OPEn) components. The phase behavior in the neighborhood of the L2 phase is investigated for ternary (cyclohexane/H2O) and quaternary (cyclohexane/H2O/n-hexanol) systems of TX-100 and OPEn (n = 5, 7 and 9). The extent of the L2 domain and the maximum amount of water wo,max that can be solubilized by isotropic solutions strongly depend on the concentration and the length (n) of the polar chain of the surfactant, temperature, and the amount of n-hexanol present. Depending on these variables, with increasing wo (molar ratio of water to surfactant) some of the following phase transitions occur: L2 → LC → L → liquid/gel → gel. Except for the liquid crystalline LC phase, all phases involved are optically isotropic, and the liquid L phase is most likely bicontinuous. Since n-hexanol is a better solvent than cyclohexane for both the surfactant and water, it destabiliz...