1-methylimidazolium Acetate Research Articles

Comparative analysis of dielectric spectra in protic ionic liquids: Experimental findings and computational molecular decomposition

Using a combination of experimental measurements and polarizable molecular dynamics simulations, we investigate the dielectric spectra of the protic ionic liquid 1-methylimidazolium acetate, shedding light on their dynamic behavior and intermolecular interactions when adding 1-methylimidazolium trifluoroacetate to increase the fraction of a strong Brønsted acid in the system. The comparison between experimental and computational results provides valuable insights into the accuracy of the simulation models (with and without explicit proton transfer) and the ability to capture the intricate dynamical features of the protic ionic liquid. The investigation revealed complete deprotonation of trifluoroacetate, inducing a shift in the ionic liquid towards a more pronounced ionic state. The computational decomposition of the dielectric spectra into molecular translational and rotational contributions unveiled a reduction in the dielectric constant. This reduction was primarily ascribed to a decrease in translational contributions. Additionally, a strong correlation of the mutual orientation of molecules was found. The observed rise in conductivity upon the addition of 1-methylimidazolium trifluoroacetate to the system was attributed to an increase in proton transport.

On the Rich Chemistry of Pseudo-Protic Ionic Liquid Electrolytes.

Mixing weak acids and bases can produce highly complicated binary mixtures, called pseudo-protic ionic liquids, in which a complex network of effects determines the physicochemical properties that are currently impossible to predict. In this joint computational-experimental study, we investigated 1-methylimidazole-acetic acid mixtures through the whole concentration range. Effects of the varying ionization and excess of either components on the properties, such as density, diffusion coefficients, and overall hydrogen bonding structure were uncovered. A special emphasis was put on understanding the multiple factors that govern the conductivity of the system. In the presence of an excess of acetic acid, the 1-methylimidazolium acetate ion pairs dissociate more efficiently, resulting in a higher concentration of independently moving, conducting ions. However, the conductivity measurements showed that higher concentrations of acetic acid improve the conductivity beyond this effect, suggesting in addition to standard dilution effects the occurrence of Grotthuss diffusion in high acid-to-base ratios. The results here will potentially help designing novel electrolytes and proton conducting systems, which can be exploited in a variety of applications.

Enhancing CO2/(light gases) separation performance of Pebax-based mixed-matrix membranes by [BMIM][AC] ionic liquid

Incorporating the proper additive with an affinity towards target gases is considered a helpful strategy for simultaneously improving membrane permeability and selectivity. In this research, the superior features of polyetherblockamide polymer (Pebax1657), 1–Butyl3–methylimidazolium acetate ([BMIM][AC]) ionic liquid (IL), and aluminum oxide (Al2O3) nanoparticles were blended to produce efficient ternary mixed-matrix membranes for CO2 removal from light gases. The fabricated membranes structures have been evaluated by FTIR3ATR, FESEM, XRD, and DSC analyses. The permeation rates of unmixed CH4, N2, and CO2 gases through the resulting membranes were obtained at 25 °C and a feed pressure range of 4–10 bar. The gas permeability results showed that embedding Al2O3 nanoparticles as the loading up to 6 wt% increased the CO2/(light gases) separation performance. Besides, adding the IL into the polymer matrix boosted the membranes gas separation efficiencies caused by the increased CO2 solubility and their fractional free volume. The results also revealed that the resulting membrane containing 15 wt% of [BMIM][AC] IL and 6 wt% of Al2O3 nanoparticles, which has the best gas separation efficiency, is the optimum ternary mixed-matrix membrane. The comparison between the optimized membrane and the unloaded one efficiencies demonstrated that CO2/N2 and CO2/CH4 selectivities, along with the CO2 permeability, rose from 63.40, 19.93, and 115.39 Barrer for the unloaded membrane to 81.18, 25.14, and 166.42 Barrer for the optimum membrane (around 28 %, 26 %, and 44 % increments), at 10 bar and 25 °C, respectively.

Dissolution dynamics of woven all-silk composites fabricated in the ionic liquid 1-ethyl-3-methylimidazolium acetate

Single layer woven all-silk composites (ASCs) have been prepared using the ionic liquid 1-ethyl-3- methylimidazolium acetate ([C2mim][OAc]), with the dissolution carried out under various times and temperatures. Cross sectional images revealed the dissolved and coagulated silk matrix were formed along both fibre directions with thicker matrix layer observed along warp direction. Radial integration utilising the second Legendre polynomial function (P2) were conducted on the collected intensity distribution curves attained from WAXD azimuthal scans, enabling the quantitative measurement of the average orientation of crystals. A simple linear mixing rule was employed to correlate the coagulated matrix (Vm) with respective P2 values, leading to the calculation of Vm. Time–temperature superposition (TTS) was verified through the construction of master curves, from which the dissolution was found to have Arrhenius-like behaviour allowing the determination of dissolution activation energy (Ea). The three measured tensile properties were all found to follow TTS principle, thus yielding another two methods to determine Ea. Five different methods point to an average Ea value of 93±2 kJ/mol. Additionally, the dissolution rates and activation energies of single and woven silk were compared. The master curves constructed in this study may provide a guidance for future design of silk fibre reinforced composites with desired properties.

Ionic liquid–controlled growth of bifunctional NiCo2O4 nanostructures with different dimensionalities on carbon cloth for oxygen evolution reaction and asymmetric supercapacitor

The design structure of electrocatalysts/electrode materials is important for achieving highly efficient energy conversion and storage in electrochemical energy devices. We report the synthesis of 3D NiCo2O4 hierarchical nanocactus arrays (NiCo2O4–NC) comprising 1D nanowires and 2D nanoflakes on carbon cloth by controlling the concentration of ionic liquid (IL) 1–dodecyl–3–methylimidazolium acetate ([C12MIm]Ac). For both oxygen evolution reaction (OER) and asymmetric supercapacitors (ASC), NiCo2O4–NC shows enhanced electrochemical performance. Impressively, for the OER process, NiCo2O4–NC exhibits an overpotential of 294 mV at 10 mA cm−2, Tafel slope of 77 mV dec−1, and superior stability. As a supercapacitor electrode, NiCo2O4–NC exhibits a high specific capacitance of 1842 F g−1 at 1 A g−1, outstanding rate capability, and superior cycling stability. Moreover, NiCo2O4–NC–based ASC produces a high energy density of 46.1 Wh kg−1 at power density of 557.4 W kg−1. The outstanding electrochemical performance is attributed to the distinct structure of NiCo2O4–NC with the merits of both 1D nanowires and 2D nanoflakes. This work not only offers an effective mean to design nanostructured metal oxide arrays with improved electrochemical performance but also lays the foundation of studying the application potential of ILs in the synthesis of multifunctional materials.

Fabrication of ionic liquid stabilized MXene interface for electrochemical dopamine detection.

Development of MXene (Ti3C2Cl2)-based sensing platforms by exploiting their inherent active electrochemistry is highly challenging due to their characteristic poor stability in air and water. Herein, we reporta cost-effective methodology to deposit MXene on aconductive graphitic pencil electrode (GPE). MXenes can provide active surface area due to their clever morphology of accordion-like sheets; however, the disposition to stack together limits their potential applications. A task-specific ionic liquid (1-methyl imidazolium acetate) is utilized as a multiplex host material to engineer MXene interface via π-π interactions as well as to act as a selective binding site for biomolecules. The resulting IL-MXene/GPE interface proved to be a highly stable interface owing to good interactions between MXene and IL that inhibited electrode leaching and boosted electron transfer at the electrode-electrolyte interface. It resulted in robust dopamine (DA) oxidation with amplified faradaic response and enhanced sensitivity (9.61 µA µM-1cm-2) for DA detection. This fabricated sensor demonstrated large linear range (10µM - 2000µM), low detection limit (702nM), high reproducibility, and good selectivity. We anticipate that such platform will pave the way for the development of stable and economically viable MXene-based sensors without sacrificing their inherent properties. Scheme 1 Schematic illustration of the IL-MXene/GPE fabrication and oxidative process towards non-enzymatic dopamine sensor.

Polarizable molecular dynamics simulations on the conductivity of pure 1-methylimidazolium acetate systems

The protic ionic liquid 1-methylimidazolium acetate is in equilibrium with its neutral species 1-methylimidazole and acetic acid. Although several experimental data indicate that the equilibrium favors the neutral species, the system exhibits a significant conductivity. We developed a polarizable force field to describe the ionic liquid accurately and applied it to several mixtures of the neutral and charged species. In addition to comparing single values, such as density, diffusion coefficients, and conductivity, with experimental data, the complete frequency-dependent dielectric spectrum ranging from several MHz to THz can be used to determine the equilibrium composition of the reaction mentioned above.

Emulating proton transfer reactions in the pseudo-protic ionic liquid 1-methylimidazolium acetate.

Proton transfer reactions can enhance conductivity in protic ionic liquids. However, several proton reactions are possible in a multicomponent system of charged and neutral species, resulting in a complex reaction network. Probabilities and equilibrium concentrations of the involved species are modeled by the combination of reducible Markov chains and quantum-mechanical calculations.

Deciphering Solvation Effects in Aqueous Binary Mixtures by Fluorescence Behavior of 4-Aminophthalimide: The Comparison Between Ionic Liquids and Alcohols as Cosolvents.

Ionic liquids (ILs) have received attention for many years due to them being very promising as green solvent substitutes, but they are not fully understood, especially their behavior dissolved in other solvents, for example, water. Thus, the goal of this contribution is to show insight into the different IL-water mixtures interaction. In this way, two protic ILs (PILs), ethylammonium nitrate (EAN) and 1-methylimidazolium acetate (MIA), mixed with water were investigated. To study the PILs-water interaction, the unique spectroscopical behavior in water of the molecular probe 4-aminophthalimide (4-AP) was used. 4-AP emission spectra show hypsochromic shifting by changing the excitation wavelength and, using time-resolved spectroscopy, can be detected by a blue shifting with time. Also, the water mixture of an aprotic IL, 1-methyl-3-butylimidazolium tetrafluoroborate (bmimBF4), and three alcohols, methanol (MeOH), 2-propanol (2-PrOH), and t-butanol (t-BOH), were investigated for comparison. Our results show that the water-ILs interaction is dominated by the size of the IL components, in particular, the cation size. Thus, in MIA-water and bmimBF4-water mixtures, 4-AP is mostly solvated by the IL, even at a low IL molar fraction, as in the t-BOH-water mixture. This finding is especially interesting when ILs-water mixtures are used as a solvent in an organic reaction, where it may call attention to water probably not being the solvent that is interacting with the reactants.

Determination of intrinsic viscosity of native cellulose solutions in ionic liquids

The weight-average molecular weights of six native cellulose samples in ionic liquids were determined through steady shear viscosity measurements in the ionic liquid butyl methyl imidazolium chloride. The intrinsic viscosity [η] in ethyl methyl imidazolium acetate (EMImAc) is measured using a gravity-driven glass capillary viscometer and found to be independent of temperature in the range of 30–80 °C, disproving a literature report of [η] in EMImAc, exhibiting a strong temperature dependence. Findings are contrasted with values of intrinsic viscosity in cupriethylenediamine hydroxide, the most widely used solvent to dissolve and analyze the molecular weight of cellulose pulps in industry. Differences are tentatively attributed to the different temporary association properties of cellulose chains in the two solvents. Finally, it is demonstrated that cellulose adsorbs at the air/solution interface in three different ionic liquids to create a viscoelastic liquid interfacial layer of higher concentration. Adsorption at the air/solution interface gives an extra contribution to the measured torque in various rotational rheometer geometries, which apparently simply adds to the torque from the pure bulk solution.

Design and optimization of the efficient extractive distillation process for separating the binary azeotropic mixture methanol-acetone based on the quantum chemistry and conceptual design

The contribution of this work is proposing a systematic approach to design an efficient extractive distillation (ED) process for separating binary azeotropic mixture, which including the study of σ-profiles, the analysis of thermodynamic topology, and the investigation of economic validation. The separation of methanol-acetone azeotrope serves as the case study to demonstrate the effectiveness of the proposed method. Firstly, the σ-profiles is employed to select appropriate candidates of ILs via the analysis of interaction between five cations and eight anions. Then, the feasibilities of two candidates ILs (i.e., 1-Methylimidazolium acetate ([MIM][OAc]) and 1-methylimidazolium 2-hydroxypropionate ([MIM][Hpr])) and DMSO are further studied by the thermodynamic topological analysis with residue curve maps and univolatility lines. Finally, the design and optimization of ED with the three potential entrainers are conducted to prove the validity of the proposed method. The results demonstrated that the ED process with [MIM][Hpr] is the most economical process compared with [MIM][OAc] and DMSO indicating that the proposed approach is appropriate for screening entrainer to separate such mixture. Moreover, the proposed comprehensive methodology in this work is a valuable protocol, which could be extended to separate other azeotropic systems by using an energy-saving ED process.

Binary Mixtures of Aprotic and Protic Ionic Liquids Demonstrate Synergistic Polarity Effect: An Unusual Observation

In this communication, we demonstrate the solute–solvent and solvent–solvent interactions in the binary mixtures of two aprotic ionic liquids, namely 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, with the protic ionic liquid 1-methylimidazolium acetate. The synergistic effects as expressed by the solvatochromic parameter are noted. This observation is in contrast to the mixing of protic ionic liquids 1-methylpyrrolidium acetate and 4-methylmorpholine acetate with 1-methylimidazolium acetate, respectively. It appears that the synergistic effects in the binary mixtures of aprotic and protic ionic liquids are caused by the formation of hydrogen bonds, since cations are dominant H-bond donors while anions are dominant H-bond acceptors. Preferential solvation models are used to describe the solute–solvent interactions in the binary ionic liquid mixtures.

Thermophysical characterization of sorbitol and 1–ethyl–3–methylimidazolium acetate mixtures

In this study, the solubility of a sugar alcohol (sorbitol) in 1–ethyl–3–methylimidazolium acetate was measured experimentally at various temperatures. Excess Gibbs energy models were utilized for modeling of solubility. Additionally, the thermophysical properties including density and viscosity of the binary mixtures of ionic liquid and sorbitol were measured. With the application of experimental data the apparent molar volumes at infinite dilution Vϕ0, the apparent molar isobaric expansibility Eϕ0 and Hepler's constants were calculated. It was found that sorbitol behaves as structure-breaker in the ionic liquid. Moreover, the applicability of local composition models for correlation of the experimental solubility and density data was further investigated. Additionally, Arrhenius–Andrade and Vogel–Tamman–Fulcher equations were applied for correlation of the viscosity measurements.

On the use of methylimidazolium acetate ionic liquids as solvent and stabilizer in the synthesis of cobalt nanoparticles by chemical reduction method

1-ethyl-3-methylimidazolium acetate (EMIMOAC) and 1-buthyl-3-methylimidazolium acetate (BMIMOAC) ionic liquids have been used as a solvent and stabilizing agent in an attempt to prepare cobalt nanoparticles via chemical reduction method. The SEM and UV-Vis techniques confirm the formation of nanoparticles. XRD reveals the nanocrystalline nature of the products with average crystallite size of 27.5 and 24.1 nm for CoEMIMOAC and CoBMIMOAC, respectively. The SEM and EDAX morphological/atomic weight ratio analyses show not much difference between the nanocrystals formed in EMIMOAC or BMIMOAC. These results indicate that the cationic part of the ionic liquid did not play significant role during nucleation and growth of the particles. The zone of inhibition of CoEMIMOAC obtained against Staphylococcus aureus and Escherichia coli are 23 and 14 mm, respectively whereas that of CoBMIMOAC against the bacterial under investigation is 15 mm. The synthesized nanocrystals have therefore demonstrated great potentials as nanodrugs in the treatment of infections caused by gram-positive microorganisms.

Synthesis and characterization of imidazolium ILs based chitosan–tripolyphosphate microparticles

In this work, two imidazolium based ILs, 1–butyl–3– methylimidazolium hydrogen sulfate [bmim][HSO4] and 1–butyl–3– methylimidazolium acetate [bmim][Ac] were blended with Chitosan (CS) to synthesize the CS–IL–TPP microparticles. The prepared microparticles were characterized by Zetasizer, FTIR, TGA, SEM and elemental analysis (EDX). The addition of these ILs resulted in controlled sized microparticles which possessed good thermal stability. The elemental analysis indicated that the better crosslinking of tripolyphosphate (TPP) with CS was achieved in the presence of IL, [bmim] [Ac] as compared with [bmim] [HSO4] and CS–TPP formulation alone. The better crosslinking might result in the formation of stable and compact microparticles which could have a better control over the drug release applications. Therefore, this kind of IL might be suitable for improving the characteristics of chitosan as a drug carrier which could ultimately provide controlled release of unstable drugs.

Carbon/GO Composite Electrodes and Electrospun Polyacrylonitrile Nanofibrous Electrolyte Membranes Doped with Halogen-Free Imidazole-Based Ionic Liquid for Supercapacitor Device Fabrication

In this paper, we report the preparation of 1-methylimidazolium acetate (MIMOAc) through solvent-free sonochemical synthesis and its characterization using1H-NMR,13C-NMR and FTIR-ATR spectroscopy. Its effects on the morphological, structural and electrochemical properties of electrospun polyacrylonitrile (PAN) fibers were also investigated. SEM and AFM results showed that the MIMOAc-doped PAN fibers produced are thinner than that of the pristine PAN hence allowing more surface area for ion mobility. Its electrochemical performance compared well to the obtained results in preference to the conventional 1M KOH(aq)as aqueous electrolyte. The fabrication of a novel supercapacitor prototype following an electrical double-layer capacitor configuration assembled by mechanically pressing the electrospun MIMOAc/PAN nanofiber membranes between two activated carbon/graphene oxide (GO) composite electrodes on ITO-coated glass current collectors was presented in detail.

Properties and Structure of Cellulosic Membranes Obtained from Solutions in Ionic Liquids Coagulated in Primary Alcohols

Abstract This paper presents the results of studies on the preparation of cellulosic membranes, from a solution in 1-ethyl-3- methylimidazolium acetate (EMIMAc), using the phase inversion method. Initially, the membranes were obtained by coagulation of the polymer film in water and primary alcohols (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol), 1-hexanol, 1-octanol) resulting in membranes with significantly differing morphologies. Subsequently, composite membranes were produced, with the support layer being a membrane with the largest pores, and the skin layer a membrane with smaller pores. The resulting membranes were tested for physicochemical and transport properties. The morphology of the membrane surfaces and their cross-sections were investigated by using a scanning electron microscope (SEM). The structure of the membranes, on the other hand, was investigated by FTIR spectroscopy and WAXS structural analysis.

Effect of urea addition on chitosan dissolution with [Emim]Ac-Urea solution system

Chitosan dissolution system with [Emim]Ac (1-​ethyl-​3-​methylimidazolium acetate) and urea was designed for homogeneous chemical modification of chitosan. Physicochemical properties of [Emim]Ac and [Emim]Ac-urea, such as density, solvatochromic parameters etc, were thoroughly investigated. NMR and FTIR spectra of [Emim]Ac-Urea solution were tested for determination of interaction between [Emim]Ac and urea. Obvious chemical shift change (Δd) of typical atoms (H2, H11, C10, and C12) in [Emim]Ac-urea indicated that strong hydrogen bonds were formed between [Emim]Ac and urea. Chitosan dissolution performance in [Emim]Ac-Urea solution was studied. Density functional theory (DFT) simulations were carried out to discuss the interactions between [Emim]Ac, urea, and chitosan. Four kinds hydrogen bonds (CH/O, CH/N, NH/O, NH/N), and eight hydrogen bonds, were formed in chitobiose-[Emim]Ac-urea. In particular, anion acetate of [Emim]Ac, hydrogen atoms and nitrogen of urea formed strong hydrogen bonds with oxygen atoms, amide, and hydroxyl in chitobiose. The information obtained would provide a guide for the development of novel solvent systems for chitosan dissolution and homogeneous chemical modification.

Effect of Recycled Imidazolium-based Ionic Liquids on Biomass from Rubber Wood

Background: Ionic liquids could be used as a potential solvent to dissolve rubber wood. This is one the most successful methods for the dissolution of rubber wood. Methods: In this study, various imidazolium-based ionic liquids with different anions, e.g acetate, chloride, dycanimide and ethylphosphonate were used to dissolve rubber wood and showed that 1-ethyl-3- methyl imidazolium acetate ([Emim][OAc]) could be recycled four times. There was a small decrease in the cellulose and lignin mass regenerated of the rubber wood using recycled ionic liquids compared to fresh ionic liquids. This method had achieved a recovery ionic liquid efficiency of 90% and the Fourier Transform Infrared (FTIR) and X-Ray Diffraction (XRD) showed that the crystallinity of the cellulose through the recycled ionic liquid has significantly decreased. The yield of the conversion of cellulose to glucose increased as the number of ionic liquid cycles increased, especially at the fourth instance of recycling. On the other hand, Thermogravimetric Analysis (TGA) and 1H NMR (nuclear magnetic resonance) spectroscopy showed no structural changes in the recovered ionic liquids. Conclusion: This work proves that [Emim][OAc] has an excellent reusability. Keywords: Ionic liquids, dissolution, rubber wood, recycle, pre-treatment, anions.

Cellulose/carrageenan/TiO2 nanocomposite for adsorption and photodegradation of cationic dye

Cellulose/carrageenan/TiO2 nanocomposites were simply prepared by the co-dissolution of cellulose and carrageenan, and the dispersion of TiO2 in 1-ethyl-3- methylimidazolium acetate, followed by reconstitution with anti-solvents. The cellulose/carrageenan/TiO2 composite showed a much higher adsorption capacity for methylene blue (MB) than the cellulose and cellulose/TiO2 composite. The cellulose/carrageenan/TiO2 composite also degraded MB more efficiently in aqueous solution than the cellulose/ TiO2 composite. The MB adsorption capacity of the cellulose/carrageenan/TiO2 composite increased linearly with increasing carrageenan content in the composites.