Influence of surfactant amphiphilicity on the phase behavior of IL-based microemulsions.

In this work, we report on the phase behavior of 1-ethyl-3-methyl-imidazolium-ethylsulfate ([emim][etSO(4)])/limonene/polyethylene glycol tert-octylphenyl ether (Triton X-114 or TX-114) microemulsions as a function of ionic liquid (IL) content and temperature. Phase diagrams, conductivity measurements, and small angle X-ray scattering (SAXS) experiments will be presented. A hydrophilic IL, instead of water is used with the goal to enlarge the temperature range on which stable microemulsions can be formed.

Oligoether carboxylates: task-specific room-temperature ionic liquids.

Recently, a new family of ionic liquids based on oligoether carboxylates was introduced. 2,5,8,11-Tetraoxatridecan-13-oate (TOTO) was shown to form room-temperature ionic liquids (RTILs) even with small alkali ions such as lithium and sodium. However, the alkali TOTO salts suffer from their extremely high viscosities and relatively low conductivities.

[emim][etSO4] as the polar phase in low-temperature-stable microemulsions.

We demonstrate here that microemulsions with an IL as the continuous phase can be formed so that they are stable over a wide temperature range and have intermediary properties between flexible and stiff microemulsions. Three components (1-ethyl-3-methylimidazolium ethylsulfate ([emim][etSO(4)]), limonene, and octylphenol ethoxylate (Triton X 100, abbreviated as TX-100)) were used. This ternary system has been characterized from ambient temperature down to -10 °C by means of conductivity, viscosity, and small-angle X-ray scattering (SAXS) measurements.

Correlation between polarity parameters and dielectric properties of [Na][TOTO]--a sodium ionic liquid.

The ionic liquid (IL) [Na][TOTO], with sodium as the cation and an oligoethercarboxylate as the anion, shows properties that differ significantly from conventional ionic liquids, like imidazolium salts. Its polarity, determined in the temperature range of (293-333) K from measurements of Reichardt's E value and the Kamlet-Taft parameters is extraordinarily low and matches the dielectric constant extrapolated from frequency dependent complex permittivity measurements. The dielectric spectra also reveal split dynamics with the dominating slow mode probably associated with the reorientation of -COO(-).

Ethylammonium nitrate in high temperature stable microemulsions.

The increasing number of publications reflects the still growing interest in nonaqueous microemulsions containing room-temperature ionic liquids. Recently, we characterized microemulsions composed of the room-temperature ionic liquid ethylammonium nitrate (EAN) as polar phase, dodecane as continuous phase and 1-hexadecyl-3-methyl imidazolium chloride ([C(16)mim][Cl]), an IL that exhibits surfactant properties, and decanol as cosurfactant at ambient temperature. We demonstrate here the high thermal stability of these microemulsions.

Catanionic micelles as a model to mimic biological membranes in the presence of anesthetic alcohols.

We show here the influence of n-alcohols (C(2)OH-C(8)OH) on the solubility behavior of cationic-anionic surfactant mixtures, so-called "catanionics". We studied catanionics of different compositions composed of sodium dodecyl sulfate (SDS)/cetyltrimethylammonium bromide (CTAB) and sodium dodecanoate (SDod)/CTAB mixtures. Interestingly, with a molar excess of SDS, long chain n-alcohols (C(4)OH-C(8)OH) significantly depress the solubility temperature of the SDS+CTAB catanionic and increase the kinetic stability of the solution.

Microemulsions with an ionic liquid surfactant and room temperature ionic liquids as polar pseudo-phase.

In this investigation we present for the first time microemulsions comprising an ionic liquid as surfactant and a room-temperature ionic liquid as polar pseudo-phase. Microemulsions containing the long- chain ionic liquid1-hexadecyl-3-methyl-imidazolium chloride ([C16mim][Cl]) as surfactant, decanol as cosurfactant, dodecaneas continuous phase and room temperature ionic liquids (ethylammonium nitrate (EAN) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]][BF4]), respectively) as polar microenvironment have been formulated. The phase diagrams of both systems were determined at a constant surfactant/cosurfactant molar ratio.