Hydrophilic Ionic Liquid Research Articles

Phase separation behaviors of polyethersulfone/ionic liquid blends and the correlation with the physical properties

Polyethersulfone (PES) is a widely used membrane material which shows excellent comprehensive performance, but the inherent hydrophobicity greatly limits its applications. Herein, we modified the PES with a hydrophilic ionic liquid, 1-vinyl-3-butylimidazole tetrafluoroborate, IL(BF4), by melt blending. The phase behavior and properties of the PES/IL(BF4) binary blends were investigated systematically. It was found that the sulfone group on PES can form a hydrogen bond with the H atom at the C-2 position of the imidazole ring of ionic liquid, which makes the good compatibility between PES and IL(BF4). Nuclear magnetic resonance (NMR) confirmed the existence of hydrogen bonding between PES and IL(BF4). It was further found that the homogenous PES/IL(BF4) blends undergo phase separation with increasing temperature and the blends have the typical lower critical solution temperature (LCST) phase behaviors. Small angle X-ray scattering analysis confirmed the microphase separation of the blends during the annealing at elevated temperature and the formation of the IL(BF4) enriched domains dispersed in PES matrix. In situ Fourier transform infrared spectroscopy (FTIR) revealed that such phase separation was attributed to the weakening of the hydrogen bonding with increasing temperature. Moreover, the addition of IL(BF4) endows the homogeneous PES/IL(BF4) blends with hydrophilicity and electrical conductivity; while the phase separation leads to the enhanced hydrophilicity and decreased electrical conductivity because of the enrichment of the IL(BF4).

Efficient Separation of Proteins and Polysaccharides from Dendrobium huoshanense Using Aqueous Two-Phase System with Ionic Liquids.

By applying the hydrophilic ionic liquid, 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), and inorganic salts (K3PO4), an ionic liquid aqueous two-phase system (ILATPS) was established for the separation of Dendrobium huoshanense polysaccharides (DhPs) and proteins. The effects of inorganic salt concentration, IL quantity, crude DhPs concentration, pH value and temperature were studied to achieve the optimal condition. With the best combination of ILATPS (1.75 g K3PO4, 1.25 g [C4mim]Cl, 10 mg crude DhPs and 5.0 mL ddH2O at pH 7.0 under 25 °C), the extraction efficiency rates for DhPs and proteins were 93.4% and 90.2%, respectively. The processed DhPs retrieved from the lower salt-rich phase comprised mannose, glucose, galactose, arabinose, and galacturonic acid with a molar ratio of 185:71:1.5:1:1 and the molecular weight was 2.14 × 105 Da. This approach is fast, simple and environmentally friendly. It provides a new insight into purifying functional polysaccharides of plant origin.

Application of a reversed-phase ionic liquid dispersive liquid-liquid microextraction method for the extraction and preconcentration of domoic acid from urine samples

A simple and efficient sample extraction and preconcentration method based on reversed-phase ionic liquid dispersive liquid-liquid microextraction (RP-IL-DLLME) had been developed and used to quantify the domoic acid in human urine samples. The analysis was performed by ultra-performance liquid chromatography and photodiode array detection. During the procedure, hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim] BF4 as dispersive solvent and NaOH solution was chosen as extraction solvent. Some important parameters in the method were investigated to get high enrichment factors. Under optimal conditions, the linearity of the method was in the range of 0.1–10 ng mL−1 and the correlation coefficient was above 0.9996. The relative standard deviations (RSDs) of the developed methods for intra-day (n = 5) and inter-day (n = 5) precision ranged from 1.9 to 3.9%. Meanwhile, limit of detection (LOD) was 0.03 ng mL−1(S/N = 3) and that of quantification (LOQ) was 0.1 ng mL−1(S/N = 10) with the enrichment factors (EF) being 230. Eventually, the proposed method was successfully applied to the determination of Dominic acid in human urine samples.

Thermodynamic analysis of H2O − 3-aminopropyl tributyl phosphonium glycinate as a working pair for absorption refrigeration system

In this paper, A hydrophilic dual amino-functionalized ionic liquid 3-aminopropyl tributyl phosphonium glycinate ([aP4443][Gly]) with high thermal stability was used as absorbent and the refrigerant was water for the absorption refrigeration system (ARS). The heat capacities of the system were estimated by the differential scanning calorimetry (DSC) with various water mass fractions (w1) (0.004 to 0.6993) and temperatures (285 K to 365 K), and a polynomial equation on temperature and mass fraction of ionic liquid (w2) was associated. Between the experimental and estimated values, the average relative deviation (ARD) was 0.66%. The vapor–liquid equilibrium (VLE) data of the H2O–[aP4443][Gly] binary mixture was correlated using the electrolyte nonrandom two-liquid (eNRTL) model, and the binary mixture's excess thermodynamic properties were simulated. The first and second laws of thermodynamics were used to simulate the performance of a single-effect ARS with a solution heat exchanger (SHE). The ARS simulation results show that the coefficient of performance (COP) of the system with H2O–[aP4443][Gly] as the working pair is higher than that of the conventional working pair NH3-H2O but slightly lower than that of H2O-LiBr. Furthermore, the effect of generator temperature (Tg) on ARS is investigated; simulation results show that the ARS of the novel working pair has a higher COP value at higher generator temperature, indicating that H2O–[aP4443][Gly] has the potential to be a new type of absorption refrigeration working pair.

Bis-polyethylene glycol-functionalized imidazolium ionic liquids: A multi-method approach towards bulk and surface properties

Adding to the versatile class of ionic liquids, we report a new series of hydrophilic polyethylene glycol-functionalized room-temperature ionic liquids, offering interesting thermo- and electrochemical behavior as well as remarkable surface properties. A scalable and generally applicable synthetic procedure for the preparation of N,N’-bis(polyethylene glycol)imidazolium salts, generally abbreviated as [(mPEGn)2Im][A] (n = 2‒6, A = I‒, OMs‒, PF6‒, NTf2‒) was developed. These ionic liquids were studied concerning their thermo- and electrochemical properties, such as phase transition behavior, decomposition temperature, viscosity, and density, as well as electrical conductivity and electrochemical stability, using i.a. differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Additionally, the surface properties were investigated by angle-resolved X-ray photoelectron spectroscopy (ARXPS) and the pendant drop method. Molecular dynamics simulations complement the studies and provide insight into the molecular structure of the ionic liquids and their specific orientation at the liquid-vacuum interface.

Reaction-extraction platforms towards CO2-derived cyclic carbonates catalyzed by ionic liquids

This work systematically monitors the keys to understand the applicability of two close-cycle processes recently proposed that enable the regeneration of homogeneous catalysts based on ionic liquids by liquid-liquid extraction. It aims at looking for more efficient CO2 conversion platforms to prevent global warming. The universal character of these two platforms is here demonstrated for a substrate scope that accounts the 7 most representative cyclic carbonates of the literature and 17 ionic liquids that play the role of efficient homogeneous catalysts. Water-based platform proves to be more appropriate for separating hydrophilic IL catalysts from less polar and hydrophobic carbonates, improving the energy consumption when compared with distillation as benchmark separation approach in the literature. On the contrary, hydrophobic ionic liquids enhance the process combined with fatty alcohols to produce hydrophilic cyclic carbonates and drastically reduce energy consumption at reasonable lower product specifications when compared with benchmark process. Overall, liquid-liquid extraction stands out as a more efficient process scheme to separate cyclic carbonates from homogeneous catalysts based on ionic liquids.

Au(111) in [Mppip][Tfsi] in Dependence of Water Content: Revealing the Initial Stages of Cathodic Corrosion Using in-Situ STM

Cathodic corrosion was first observed by Fritz Haber at the end of the 19th century,[1] and was nearly forgotten for a long time, but has recently returned as an important research topic.[2,3] The prospects to form nanoparticles of noble metals and to restructure metal surfaces, in particular, stirred researchers’ interest.[4,5] Moreover, cathodic corrosion may hinder other processes such as metal deposition that occur at highly negative potentials. As ionic liquids have desirable properties of being stable over a relatively wide potential window coupled with low ion mobility, these electrolytes are often used for studies of processes at very low electrode potentials, for example, the deposition of metals with low reduction potentials such as lithium or sodium.[6,7] Unfortunately, if an electrode is cathodically corroded at potentials positive of the onset of metal deposition, this is of little use. Therefore, it is crucial to understand and thus prevent the initial stages of cathodic corrosion in such systems. In-situ scanning tunneling microscopy (STM) was used to study cathodic corrosion of a Au(111) surface in the hydrophobic ionic liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ([MPPip][TFSI]) with various water contents. It has been observed that the onset potential of cathodic corrosion is highly dependent on the presence and the amount of water. This notable role of water has been found already for cathodic corrosion of Au in aqueous methanolic alkali metal hydroxide electrolytes:[8] the higher the water content, the more positive the onset potential. Cathodic corrosion of Au(111) begins at the so-called elbows of the herringbone reconstruction, which can lead to a characteristic pattern of equidistant holes. In hydrophilic ionic liquids, a similar process has already been observed.[9] In contrast, for the hydrophobic ionic liquid [MPPip][TFSI], the pits did not merge with time, instead, the number of pits slowly increased. Furthermore, the number of pits formed during this process was observed to increase with the increase of water content. Further studies are planned to elucidate the dependence of preparation procedure, as well as experimental constituents and contaminants on the cathodic corrosion of Au(111) in the ionic liquid [MPPip][TFSI]. Such studies can help to understand if cathodic corrosion can be induced by the ionic liquid itself or only by contaminants such as water. It is known that adsorbed hydrogen plays a major role in the process[3] and it has been reported that in the absence of water cathodic corrosion is not taking place.[10] On the other hand, other studies proposed that the presence of water is not obligatory if hydrogen can be formed in another way than water reduction, for example by reduction of the IL cation.[11] References [1] F. Haber, Zeitschrift für Anorg. Chemie 1898, 16, 438–449.[2] Y. I. Yanson, A. I. Yanson, Low Temp. Phys. 2013, 39, 304–311.[3] T. J. P. Hersbach, M. T. M. Koper, Curr. Opin. Electrochem. 2021, 26, 100653.[4] T. J. P. Hersbach, V. A. Mints, F. Calle-Vallejo, A. I. Yanson, M. T. M. Koper, Faraday Discuss. 2016, 193, 207–222.[5] M. M. Elnagar, J. M. Hermann, T. Jacob, L. A. Kibler, Electrochim. Acta 2021, 372, 137867.[6] C. A. Berger, M. U. Ceblin, T. Jacob, ChemElectroChem 2017, 4, 261–265.[7] R. Wibowo, L. Aldous, E. I. Rogers, S. E. Ward Jones, R. G. Compton, J. Phys. Chem. C 2010, 114, 3618–3626.[8] M. M. Elnagar, T. Jacob, L. A. Kibler, Electrochem. Sci. Adv. 2021, accepted.[9] A. V. Rudnev, M. R. Ehrenburg, E. B. Molodkina, A. Abdelrahman, M. Arenz, P. Broekmann, T. Jacob, ChemElectroChem 2020, 7, 501–508.[10] M. M. Elnagar, J. M. Hermann, T. Jacob, L. A. Kibler, ECS Meet. Abstr. 2020, MA2020-01, 1011–1011.[11] F. Lu, X. Ji, Y. Yang, W. Deng, C. E. Banks, RSC Adv. 2013, 3, 18791. Figure 1

In vitro hemocompatibility and hemodialysis performance of hydrophilic ionic liquid grafted polyethersulfone hollow fiber membranes

Polymer-based hemodialyzers have been widely used to treat patients suffered from end stage renal disease clinically. Polyethersulfone (PES) is seen as one of the most important hemodialysis membrane materials. Numerous strategies have been done to increase the hemocompatibility of PES, but molecular chain modification of PES has been seldomly reported. In this work, a hydrophilic ionic liquid (IL) grafted PES (PES-g-IL) was used to prepare the hollow fiber membranes (HFMs). The structure and properties, including hemocompatibility, hemodialysis performance as well as the cytotoxicity of PES-g-IL HFMs were investigated systematically. It was found that PES-g-IL HFMs had higher porosity, lower protein adsorption, less platelet adhesion and longer clotting time than PES HFMs, indicating the enhanced hemocompatibility. Besides, both the toxins removal and BSA rejection of PES-g-IL HFMs were significantly higher than those of PES HFMs. Particularly, the middle molecule uremic toxin (lysozyme) clearance of PES-g-IL HFMs was twice higher than that of PES HFMs. At the same time, the BSA rejection of PES-g-IL HFMs achieved as high as 98%. Moreover, PES-g-IL showed negligible cytotoxicity. It is considered that the grafting of IL changed the microstructure and improved the hydrophilicity of PES-g-IL membranes, leading to the enhanced hemocompatibility, hemodialysis performance and cytocompatibility.

Recent developments in high-performance Nafion membranes for hydrogen fuel cells applications

As a promising alternative to petroleum fossil energy, polymer electrolyte membrane fuel cell has drawn considerable attention due to its low pollution emission, high energy density, portability, and long operation times. Proton exchange membrane (PEM) like Nafion plays an essential role as the core of fuel cell. A good PEM must have satisfactory performance such as high proton conductivity, excellent mechanical strength, electrochemical stability, and suitable for making membrane electrode assemblies (MEA). However, performance degradation and high permeability remain the main shortcomings of Nafion. Therefore, the development of a new PEM with better performance in some special conditions is greatly desired. In this review, we aim to summarize the latest achievements in improving the Nafion performance that works well under elevated temperature or methanol-fueled systems. The methods described in this article can be divided into some categories, utilizing hydrophilic inorganic material, metal-organic frameworks, nanocomposites, and ionic liquids. In addition, the mechanism of proton conduction in Nafion membranes is discussed. These composite membranes exhibit some desirable characteristics, but the development is still at an early stage. In the future, revolutionary approaches are needed to accelerate the application of fuel cells and promote the renewal of energy structure.

Universal and low energy-demanding platform to produce propylene carbonate from CO2 using hydrophilic ionic liquids

Ionic liquids (ILs) have been extensively proposed as efficient catalysts to promote CO2 cycloaddition reaction to epoxides for producing cyclic carbonates. Recently, liquid-liquid extraction with water as an enhancer approach to regenerate ILs and to purify the product was proposed, since it reduces energy consumption and enhances the neat catalytic activity of the IL due to hydroxyl groups of water. In this work, a comprehensive sample of homogeneous IL catalysts proposed in the literature is experimentally evaluated both in the catalytic step and in its separation by liquid-liquid extraction with water, to demonstrate the universality of the proposed reaction-separation proposal for hydrophilic ILs. Then the complete processes for CO2 conversion to propylene carbonate were modelled using Aspen Plus to compare the catalyst/product separation efficiency and the specific energy consumption using liquid-liquid extraction and distillation-based platforms. The energy consumption is significantly lower using liquid-liquid platform (1.1–1.3 kWh/kgPC) than distillation one (2.4–3.1 kWh/kgPC). It is concluded that hydrophilic ionic liquids, as those formed by [EtOHmim] cation and halide anions, are promising catalysts since they allow: (i) reducing the process energy consumption due to their high catalytic activity and (ii) full catalyst recovering, even at high catalyst loadings, by improving the water extractive properties for IL separation from PC.

The activity and molecular interaction of lysozyme in adding four ionic liquids aqueous solutions

In this work, four hydrophilic ionic liquids (ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim]BF4), 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), 1-butyl-3-methylimidazolium bromide ([C4mim]Br) and 1,3-dimethylimidazolium iodide ([dmim]I)) were selected to probe their effect on lysozyme activity and the molecular interaction in aqueous solutions. Specifically, the effects of pH and concentration of ILs on lysozyme activity were investigated by using the spectrophotometric turbidity assay. The results demonstrated that the effect of ILs on lysozyme activity depended on the concentration of ILs. Fixing the pH at 6.85, lysozyme activity rose firstly and then reduced with the increase of concentration of four ILs, reaching the maximum at 75 mM. The UV–Vis spectra illustrated that the interaction between ILs and lysozyme was weak. The results of emission and synchronous fluorescence spectra indicated that ILs had a quenching effect on the fluorescence of lysozyme, and the quenching effect increased with the increasing concentration of ILs. Meanwhile, the fluorescent quenching mechanism of ILs on lysozyme was dynamic quenching, and ILs had significant effects on the tryptophan (Trp) residues Trp62 or Trp108 at the active site of lysozyme, which suggested that effects of ILs on lysozyme activity could be attributed to the conformational changes of lysozyme triggered by changes in the microenvironment surrounding Trp62 or Trp108.

Preparation and Separation Properties of Electrospinning Modified Membrane with Ionic Liquid Terminating Polyimide/Polyvinylpyrrolidone@Polydopamine.

In this paper, superhydrophilic polyimide (PI) membranes were prepared using the electrostatic spinning method, capped with a hydrophilic ionic liquid (IL), and blended with polyvinylpyrrolidone (PVP). Using this preparation, the surface of the fiber membranes was coated in polydopamine (PDA) by means of an in-growth method. Scanning electron micrographs showed prepared blend films can form continuous fibers, for whom the distributions of diameter and pore were uniform. Post-modification (carried out by adding hydrophilic substances), the ability of the membrane surface to adhere to water was also significantly improved. The water contact angle was reduced from 128.97 ± 3.86° in unmodified PI to 30.26 ± 2.16°. In addition, they displayed a good separation effect on emulsified oil/water mixtures. The membrane flux reached a maximum value of 290 L·m−2·h−1, with a maximum separation efficiency reached of more than 99%. After being recycled 10 times, the separation efficiency maintained a level exceeding 95%. The purpose of this study is to demonstrate the simplicity and efficiency of this experiment, thereby providing new ideas for the future application of membrane separation technology in wastewater treatment.

Interaction between Hydrophilic Ionic Liquid and Phospholipid/Cholesterol Mixed Film.

Surface pressure (π)-area (A) isotherms were studied to analyze the interactions between a hydrophilic ionic liquid (IL) (ethyl(2-hydroxyethyl)dimethylammonium methanesulfonate) and a pure dipalmitoylphosphatidylcholine (DPPC) film or a DPPC-cholesterol mixed film. When the hydrophilic IL was added to an underlayer solution, the isotherm shifted toward higher areas. Intriguingly, when the hydrophilic IL was added, the packing of the film materials became loose and the elastic modulus decreased, resulting in increased flexibility. This phenomenon was most evident under a cholesterol mole fraction of 0.2. This composition resembles that of cell membranes, which typically comprise phospholipids and cholesterol, suggesting that this hydrophilic IL may be able to interact significantly with biological membranes.

Molecular insights into the electrowetting behavior of aqueous ionic liquids.

Molecular dynamics (MD) simulations were applied to investigate the wettability of aqueous hydrophilic and hydrophobic imidazolium-based ionic liquid (IL) nano-droplets on a graphite surface under a perpendicular electric field. Imminent transformation in the droplet configuration was observed at E = 0.08 V Å-1 both for hydrophobic ILs 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTF2] and SPC/E water droplets. However, for the hydrophilic IL, 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4], the droplet was entirely elongated to column-shaped at E = 0.09 V Å-1 for lower weight percentages of ILs and at E = 0.15 V Å-1 for a higher weight percentage of ILs (i.e., 50 wt%). We explored the impact of the electric field through various parameters such as mass and charge density distribution across the droplet, contact angle of the droplet, orientation of water dipoles, and hydrogen bond analysis. The external electric field was found to influence the orientation of water dipoles and the accumulation of charge at various interfaces was observed with an increase in an electric field, which finally leads to shape deformation and depletion of ions from the liquid-vapor interface of the droplet. However, this behavior strongly depends on the hydrophilicity or hydrophobicity of the ILs and thus, is critically examined for both the ILs.

In Vitro Hemocompatibility and Hemodialysis Performance of Hydrophilic Ionic Liquid Grafted Polyethersulfone Hollow Fiber Membranes

In Vitro Hemocompatibility and Hemodialysis Performance of Hydrophilic Ionic Liquid Grafted Polyethersulfone Hollow Fiber Membranes

Polyethersulfone Hollow Fiber Membranes with Enhanced Hemocompatibility and Hemodialysis Performance by Hydrophilic Ionic Liquid Grafting

Polyethersulfone Hollow Fiber Membranes with Enhanced Hemocompatibility and Hemodialysis Performance by Hydrophilic Ionic Liquid Grafting

Water sorption by ionic liquids: Evidence of a diffusion-controlled sorption process derived from the case study of [BMIm][OAc

The hydrophilicity of ionic liquids (ILs) could be exploited as desiccants or in sorption-driven heat transformation, yet reports of water sorption isotherms of pure ionic liquids are still scarce. Here, water sorption studies for the six pure hydrophilic ionic liquids with 1-ethyl-3-methylimidazolium [EMIm]+ or 1-butyl-3-methylimidazolium [BMIm]+ cations and acetate [OAc]−, formate [HCOO]− or lactate [Lac]− anions show a steady and high water uptake with a small hysteresis between absorption and desorption over the relative pressure range of p/p0 = 0–0.9 for the first time. Repeated static volumetric sorption measurements with different amounts or different surface area of the example IL [BMIm][OAc] reveal a slow and strongly diffusion-driven sorption process stemming from the absorption of surface-adsorbed water into the bulk IL. Extrapolation of the water uptake to very small IL amounts with negligible kinetic hindrance gives an equilibrium water uptake capacity of over 2100 mg/g(IL) at p/p0 = 0.9. Gravimetric control experiments at a relative humidity of 75.5% confirm the time-dependence with the IL surface area at the gas–liquid-interface and the amount of the IL to reach the equilibrium uptake of 1040 mg/g at p/p0 = 0.75.

Dielectric relaxation of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/toluene microemulsions: Structure transition, percolation mechanism, interfacial polarization and electrical properties of microdroplets

The dielectric relaxation spectra of the non-aqueous ionic liquid (IL) microemulsions composed of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4])/p-(1,1,3,3-tetramethylbutyl)phenoxypolyoxyethyleneglycol (TX-100)/toluene were obtained, the measured frequency is between 1 MHz and 3 GHz. A unique dielectric relaxation located at 10–100 MHz was observed. The direct current (dc) conductivity data were obtained from the total dielectric loss. Near the percolation transition, weight fraction dependence of dc conductivity and static dielectric constant, frequency dependence of permittivity and loss angle all suggest that static percolation occurs in this hydrophilic IL microemulsion. Phase boundaries of IL-in-toluene (IL/O), bicontinuous (B.C.) and toluene-in-IL (O/IL) subregions were determined by the inflection points in the dependent curve of relaxation parameters varied with weight fraction. The mechanism of this dielectric relaxation is attributed to the interfacial polarization of droplets by analyzing relaxation time with Maxwell-Wagner theory. The phase parameters, which reflect the interior properties of the spherical dispersed particle, were calculated by Hanai theory. The dependence of phase parameters on the variation of sample composition was properly explained. For O/IL subregion, the continuous phase should be an IL/TX-100 binary solvent rather than the pure IL. For IL/O subregions, a certain amount of toluene was dissolved in the droplets.

Advances Brought by Hydrophilic Ionic Liquids in Fields Involving Pharmaceuticals.

The negligible volatility and high tunable nature of ionic liquids (ILs) have been the main drivers of their investigation in a wide diversity of fields, among which is their application in areas involving pharmaceuticals. Although most literature dealing with ILs is still majorly devoted to hydrophobic ILs, evidence on the potential of hydrophilic ILs have been increasingly provided in the past decade, viz., ILs with improved therapeutic efficiency and bioavailability, ILs with the ability to increase drugs’ aqueous solubility, ILs with enhanced extraction performance for pharmaceuticals when employed in biphasic systems and other techniques, and ILs displaying low eco/cyto/toxicity and beneficial biological activities. Given their relevance, it is here overviewed the applications of hydrophilic ILs in fields involving pharmaceuticals, particularly focusing on achievements and advances witnessed during the last decade. The application of hydrophilic ILs within fields involving pharmaceuticals is here critically discussed according to four categories: (i) to improve pharmaceuticals solubility, envisioning improved bioavailability; (ii) as IL-based drug delivery systems; (iii) as pretreatment techniques to improve analytical methods performance dealing with pharmaceuticals, and (iv) in the recovery and purification of pharmaceuticals using IL-based systems. Key factors in the selection of appropriate ILs are identified. Insights and perspectives to bring renewed and effective solutions involving ILs able to compete with current commercial technologies are finally provided.

Enhancing the Thermal Stability of Ionogels: Synthesis and Properties of Triple Ionic Liquid/Halloysite/MCC Ionogels.

In this study, an ionic liquid (IL), 1-butyl-3-methylimidazolium acetate, was used to prepare ionogels with microcrystalline cellulose (MCC) and halloysite (Hal). SEM, XRD, TG, DSC, FTIR spectroscopy, conductometry and mechanical tests were used to study the morphology, structure, thermal behaviour and electrophysical and mechanical characteristics of synthesised ionogels. XRD analysis showed a slight decrease in the interlayer space of halloysite in ionogels containing MCC, which may have been associated with the removal of residual water molecules resulting from hydrophilic IL anions and polymer macromolecules. A change in conductivity and glass-transition temperature of the ionic liquid was revealed due to intercalation into halloysite (a confinement effect) and modification with cellulose. For triple IL/Hal/MCC ionogels, the characteristic thermal degradation temperatures were higher than the corresponding values for IL/Hal composites. This indicates that the synthesised IL/Hal/MCC ionogels are characterised by a greater thermal stability than those of IL/Hal systems.