Phase diagrams of two ionic liquids: hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate (bmim-PF(6)) and relatively hydrophilic 1-butyl-3-methylimidazolium tetrafluoroborate (bmim-BF(4)) in aqueous solutions of Brij 97 were determined at 25 degrees C. Two hexagonal liquid crystalline phases formed in bmim-PF(6)- and bmim-BF(4)-containing ternary systems were investigated by means of small-angle X-ray scattering (SAXS) and rheological techniques, with comparison of composition and temperature effects. From analysis of the SAXS data, bmim-PF(6) is dominantly penetrated between the oxyethylene chains of surfactant molecules, whereas bmim-BF(4) is mainly located in the water layer of hexagonal phases. The strength of the network of hexagonal phase formed in the Brij 97/water/bmim-BF(4) system is appreciably stronger than that of the Brij 97/water/bmim-PF(6) system, indicated by the smaller area of the surfactant molecule at the interface and the higher moduli (G', G' '). Temperature has a converse effect on the lattice parameters of the two hexagonal phases.

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The aqueous mixtures of an anionic surfactant (sodium dodecyl benzene sulfonate, SDBS) and an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim]BF 4 ) within a certain range of compositions can spontaneously separate into two immiscible aqueous phases (ATPS): one surfactantrich and the other ionic liquid-rich. The phase diagrams of the ternary system of the SDBS/[Bmim]BF 4 / water were drawn based on experimental data determined at 10.0, 20.0 and 30.0 C, respectively. The borderlines of the different specific regions in the diagrams were determined using turbidity titration method. The narrow two-phase region aqueous were found to be close to the water -[Bmim]BF 4 side. The formation conditions, compositions, and physicochemical properties of the aqueous two phases have been studied. The effects of temperature, surfactant and ionic liquid content on the phase separation time and phase volume ratio of the ATPS were also investigated. This phase separation phenomenon was found to be likely due to the existence of micelle aggregates with quite large size obtained by Transmission Electron Microscopy (TEM) and Steady-state Fluorescence Quenching Measurements (SFQM) methods.

The phase behavior of aqueous system of a gemini-type cationic surfactant, N,N 0 -dodecyl-2-hydroxyl-N,N,N 0 ,N 0 -tetramethyl diammonium dichloride (simply written as 12-3(OH)-12(2Cl)), has been investigated by various complementary methods. A micellar solution region, a hexagonal liquid crystal phase region and two transition regions in the phase diagram are confirmed by SAXS and polarizing microscopy. Over the concentration range, 10-40 (wt%) of 12-3(OH)-12(2Cl), the viscoelastic properties of 12-3(OH)-12(2Cl) solutions at different temperatures have been determined using steady state and frequency sweep rheological measurements. The results from the FF-TEM study are in good agreement with the predictions from steady shear and dynamic rheology in which the large difference in the rheological behavior between 12-3(OH)-12(2Cl) and 12-3(OH)-12(2Br) at the same conditions might be mainly attributed to the role of the intermolecular hydrogen bonding which occurred between the hydroxyl substituted spacers and chloride counter ion and crystallization water molecule.

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