Electrochemistry of Room-Temperature Ionic Liquids and Melts

Ionic-Liquid-Based Aqueous Two-Phase Systems Induced by Intra- and Intermolecular Hydrogen Bonds

In recent years, aqueous two-phase systems (ATPSs) have been widely used in different fields and have become an increasingly attractive subject due to their application in the separation and purification of biomolecules. In this work, the aqueous phase behavior of ionic liquids (ILs) was modulated by changing the cis-trans structure of the anion in ILs. With the same tetra-butyl-phosphine as the cation, the cis-anion exhibited upper critical solution temperature (UCST) phenomena. In contrast, the trans-anion exhibited lower critical solution temperature (LCST) phenomena. The proposed mechanism shows that the main factors responsible for these phenomena include variations in the dissociation degree with temperature and the steric hindrance of the ILs. This phase behavior combines the chemical equilibrium in a solution with the microstructure of the molecule and is useful for constructing new chemical dynamic equilibria in ATPS. As an example of its application, aqueous solutions of both ILs can be used for the efficient separation and extraction of specific amino acids. The two ATPS systems reported in this work highlight a simple, effective, and environmentally friendly method for separating small biological molecules.

Epoxy-Containing Ionic Liquids with Tunable Functionality

New types of ionic liquids (ILs) with an epoxy group on a piperidinium-type cation were successfully synthesized by the simple anion exchange reaction of a solid 1-allyl-1-(oxiran-2-ylmethyl)piperidinium bromide, which was designed in this study. Unfortunately, the physicochemical properties, e.g., viscosity and ionic conductivity, of the ILs were inferior to those of common ILs such as 1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂mim][BF₄]) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C₄mim][Tf₂N]). However, the resulting ILs are of great interest as reaction intermediates: For example, the epoxy group on the cation could react with various reagents, including CO₂. Consequently, the modification of the cation structure in the ILs was possible. This is particularly interesting because it is very difficult to modify commonly used ILs. The approach established in this article will provide a favorable synthetic route for creating novel functional ILs in the future.

Nanoemulsions with All Ionic Liquid Components as Recyclable Nanoreactors

Nanoemulsions (NEs) comprising ionic liquids (ILs); ethanolammonium formate (HO-EOAF), proliniumisopropylester dioctylsulfosuccinate ([ProC₃][AOT]), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, ([Bmim][NTf₂]) as insoluble hydrophilic, surface active, and hydrophobic components have been constructed. This novel class of colloidal formulations exhibited several contrasting properties vis-à-vis conventional water-in-oil or water-in-ionic liquid or nonaqueous NEs such as (i) spontaneous formation, (ii) thermodynamic stability and isotropic nature, (iii) decrease of droplet size with increase in polar medium concentration, and (iv) high thermal and kinetic stability. Mechanisms and characteristics for such anomalies have been investigated by physical, spectroscopic, and imaging techniques. NEs have been demonstrated as versatile recyclable nanoreactors for user-friendly synthesis of materials such as metal-organic frameworks/light harvesting hybrid systems. We anticipate that this development will lead to the construction of several other need-based "all ionic-liquid nanoemulsions" in view of the flexibility provided by the tailoring nature of ILs.

Alkylation of Methyl Linoleate with Propene in Ionic Liquids in the Presence of Metal Salts

Vegetable oils and fatty acid esters are suitable precursor molecules for the production of a variety of bio-based products and materials, such as paints and coatings, plastics, soaps, lubricants, cosmetics, pharmaceuticals, printing inks, surfactants, and biofuels. Here, we report the possibility of using Lewis acidic ionic liquids (ILs) to obtain polyunsaturated ester dimerization-oligomerization and/or, in the presence of another terminal alkene (propene), co-polymerization. In particular, we have tested the Lewis acidic mixtures arising from the addition of a proper amount of GaCl₃ (Χ > 0.5) to two chloride-based (1-butyl-3-methylimidazolium chloride, [bmim]Cl, and 1-butylisoquinolium chloride, [BuIsoq]Cl) or by dissolution of a smaller amount of Al(Tf₂N)₃ (Χ = 0.1) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][Tf₂N]. On the basis of product distribution studies, [bmim][Tf₂N]/Al(Tf₂N)₃ appears the most suitable medium in which methyl linoleate alkylation with propene can compete with methyl linoleate or propene oligomerization.

SEM observation of hydrous superabsorbent polymer pretreated with room-temperature ionic liquids

Room-temperature ionic liquid (RTIL), which is a liquid salt at or below room temperature, shows peculiar physicochemical properties such as negligible vapor pressure and relatively-high ionic conductivity. In this investigation, we used six types of RTILs as a liquid material in the pretreatment process for scanning electron microscope (SEM) observation of hydrous superabsorbent polymer (SAP) particles. Very clear SEM images of the hydrous SAP particles were obtained if the neat RTILs were used for the pretreatment process. Of them, tri-n-butylmethylphosphonium dimethylphosphate ([P_{4, 4, 4, 1}][DMP]) provided the best result. On the other hand, the surface morphology of the hydrous SAP particles pretreated with 1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂mim][BF₄]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) was damaged. The results of SEM observation and thermogravimetry analysis of the hydrous SAP pretreated with the RTILs strongly suggested that most water in the SAP particles are replaced with RTIL during the pretreatment process.