Thermodynamic Study of Aggregation of Cholinium Perfluoroalkanoate Ionic Liquids

To advance the ionic liquid (IL) platform to tailor fluorinated surfactant properties, the aim of this work is to evaluate the surfactant properties of cholinium-based salts bearing perfluoroalkanoate anions. Novel surfactant ILs containing the cholinium cation [Ch]⁺ combined with different perfluoroalkanoate anions, namely perfluoropentanoate [PFPent]⁻, perfluorohexanoate [PFHex]⁻, perfluoroheptanoate [PFHept]⁻, and perfluorooctanoate [PFOct]⁻, were synthesized. The critical micelle concentrations (CMCs) were determined using an ionic conductivity method, at different temperatures. Thermodynamic parameters of micellization were also evaluated. The results indicate that the CMC value decreases in a linear manner with the increment of the fluoroalkyl chain length in the anion. The evaluation of the thermodynamic parameters shows that the micellization is spontaneous and entropically driven and that the enthalpy of micellization is very small. It was also observed that the introduction of the cholinium cation in these surfactants allows for smaller CMC values when compared to that of other tetraalkylammonium-based surfactants with the same fluorinated anions, in short to more efficient and green surfactants. This result is probably due to counterion association and not to counterion binding to micelle surface

Density, Viscosity, and Refractive Index of Ionic Liquid Mixtures Containing Cyano and Amino Acid-Based Anions

In this work, mixtures of five ionic liquids (ILs) based on a common cation, 1-ethyl-3-methylimidazolium ([C₂mim]⁺), and amino acid anions, namely glycinate ([Gly]⁻), l-alaninate ([l-Ala]⁻), taurinate ([Tau]⁻), l-serinate ([l-Ser]⁻), and l-prolinate ([l-Pro]⁻) with 1-ethyl-3-methylimidazolium tricyanomethane, [C₂mim]­[C­(CN)₃], were prepared. The thermophysical properties, namely density, viscosity, and refractive index, of the neat ILs and their mixtures were measured in the temperature range of <i>T</i> = (293.15 up to 353.15) K. The thermal expansion coefficients were calculated for the neat ILs and were considered to be independent of temperature in the working temperature range. Overall, experimental density, viscosity, and refractive index data of the neat AAILs were in a good agreement with those reported in literature. A dramatic decrease in the viscosity was observed for the IL mixtures as the [C₂mim]­[C­(CN)₃] content increased. The obtained results indicate that mixing [C₂mim]­[C­(CN)₃] with amino acid-based ILs is a potential mean to further increase flexibility and the fine-tune capacity of the physical and chemical properties of amino acid-based ILs

Aqueous Biphasic Systems of Pyrrolidinium Ionic Liquids with Organic Acid-Derived Anions and K₃PO₄

Aqueous biphasic systems based on ionic liquids (ILs) have been researched as promising extraction and purification routes for a huge diversity of compounds. The inherent tunability offered by ILs combined with the large variety of salts available underlines the reliable phase equilibrium data. In this vein, this work presents novel aqueous biphasic systems based on the 1-butyl-1-methylpyrrolidinium cation combined with anions derived from organic acids, such as acetate, trifluoroacetate, hexanoate, adipate, and one halogenated anion, bromide, in the presence of a powerful salting out species, the inorganic salt K₃PO₄. The capacity of these ILs to undergo phase separation is discussed in regard to the chemical structure of the IL anion. The results here obtained were compared with those determined for poly­(ionic liquid) analogues, and it was observed that while in ILs the hydrophobicity of the anion has the major role in phase splitting, in poly­(ionic liquid)­s that role is played by the polymer molecular weight. The effect of temperature on the phase equilibria is addressed

Cholinium-Based Poly(ionic liquid)s: Synthesis, Characterization, and Application as Biocompatible Ion Gels and Cellulose Coatings

Cholinium-based ionic liquid methacrylic monomers having halide, lactate and acetate counter-anions were synthesized and polymerized by using conventional free radical polymerization. The polymer properties were characterized by NMR, SEC/GPC, TGA, and DSC and compared among eight different cationic polymethacrylic analogs. Polycations with different methacrylic alkylammonium backbones having lactate anion displayed comparatively better thermal stability than those having the acetate counter-anions and they also exhibited lower glass transition temperatures than their counterparts having acetate and halide counteranions. As an application, cholinium lactate methacrylate ionic liquid monomer was used to prepare ion gels by photopolymerization. Interestingly, these are the first examples of ion gels which are fully composed of low toxicity and biocompatible cholinium ionic liquids. Furthermore, the same ionic liquid monomer, cholinium lactate methacrylate, showed the ability to dissolve cellulose. This facilitated the preparation of transparent poly­(ionic liquid)/cellulose composite coatings by photopolymerization

Gas Permeation Properties of Fluorinated Ionic Liquids

Despite the increasing amount of research in the ionic liquids field, there are still quite unexplored themes. That is the case of the fluorinated ionic liquids (FILs) family, here defined as ionic liquids with fluorine tags longer than four carbon atoms. In this work, gas permeation properties of two fluorinated ionic liquids, tetrabutylammonium heptadecafluorooctanesulfonate and 1-ethyl-3-methylpyridinium perfluorobutanesulfonate, were studied. For that purpose, supported liquid membranes of the fluorinated ionic liquids were prepared using a polymeric porous membrane as supporting material, and their gas permeation properties for 10 different gases at 294 K were measured using a time-lag apparatus. The results show that the gas solubility of these FILs is of the same order of magnitude as gas solubilities for previously tested fluorinated ionic liquids and that solute size plays a more important role on gas diffusivity than viscosity. The perfluorocarbons and carbon dioxide separation performances were evaluated, and the results show that 1-ethyl-3-methylpyridinium perfluorobutanesulfonate is a better candidate than tetrabutylammonium heptadecafluorooctanesulfonate for the gas separation processes tested in this work

New Low-Toxicity Cholinium-Based Ionic Liquids with Perfluoroalkanoate Anions for Aqueous Biphasic System Implementation

This work explores the widening of properties of cholinium-based ionic liquids (ILs) through their combination with perfluoroalkanoate anions so that higher number of aqueous biphasic systems (ABSs) containing nontoxic cholinium-based ILs is available. For that purpose, six cholinium perfluoroalkanoate ILs were synthesized and their cytotoxicity was evaluated using three different animal cell lines, envisaging biotechnology applications. Ternary phase equilibrium data for ABSs composed of the cholinium perfluoroalkanoate, with fluoroalkyl chains from C₂ up to C₇, using a strong salting out agent, K₃PO₄, were determined at 25 °C. The results show the relevant role of the size of fluorinated alkyl chain length in the anion since, contrary to other ABSs containing ILs with increasing alkyl chain length in the anion, the ABSs with cholinium perfluoroalkanoates present well-spaced solubility curves, allowing the conclusion that these ABSs can be tuned by a proper choice of the IL. The phase splitting mechanism was also disclosed through water activity measurements

Study on Gas Permeation and CO₂ Separation through Ionic Liquid-Based Membranes with Siloxane-Functionalized Cations

This work explores ionic liquid-based membranes with siloxane functionalized cations using two different approaches: supported ionic liquid membranes (SILMs) and poly­(ionic liquid)–ionic liquid (PIL–IL) composite membranes. Their CO₂, CH₄, and N₂ permeation properties were measured at <i>T</i> = 293 K with a trans-membrane pressure differential of 100 kPa. The thermophysical properties of the synthesized siloxane-functionalized ILs, namely viscosity and density (data in the Supporting Information), were also determined. Contrary to what was expected, the gas permeation results show that the SILMs containing siloxane-functionalized cations have CO₂ permeabilities that are lower than those of their analogues without the siloxane functionality. The addition of siloxane-based ILs into PILs increases both CO₂ permeability and CO₂/N₂ permselectivity, although it does not significantly change the CO₂/CH₄ permselectivity. The prepared membranes present very diverse CO₂ permeabilities, between 57 and 568 Barrer, while they show permselectivities varying from 16.8 to 36.8 for CO₂/N₂ and from 9.8 to 11.5 for CO₂/CH₄. As observed for other ILs, superior CO₂ separation performances were obtained when the IL containing [C­(CN)₃]⁻ is used compared to that having the [NTf₂]⁻ anion