Imidazolium-type Ionic Liquids Research Articles

Electrical conductivity and refractive index of binary ionic liquid mixtures with diethyl carbonate, dimethyl carbonate and propylene carbonate

Four imidazolium-type ionic liquids (ILs) [Emim][NTf2], [Emmim][NTf2], [Bmim][NTf2] and [Bmmim][NTf2] have been synthesized and used to prepare binary mixtures with organic solvents dimethyl carbonate (DMC), Diethyl carbonate (DEC), and propylene carbonate (PC), respectively. The electrical conductivity and refractive index of the mixtures were measured and discussed from 293.15 to 323.15 K. The dependence of electrical conductivities of the binary mixtures on the concentration of mole fraction and temperature were fitted from the empirical Casteel-Amis (CA) equation and Vogel-Fulcher-Tamman (VFT) equation, respectively. The maximal conductivities were discussed from the fitted values for the ILs with different solvents. The dependence of refractive indexes of the binary mixtures on the concentration of mole fraction and temperature were also fitted from the Redlich-Kister polynomial equation and linear equation. Moreover, the influences of introducing methylene and methyl into the cation of ILs on their properties are discussed.

An Analytical Predictive Model for the Heat Capacity of Imidazolium-Type Ionic Liquids Derived Directly from Artificial Neural Network Modeling

An Analytical Predictive Model for the Heat Capacity of Imidazolium-Type Ionic Liquids Derived Directly from Artificial Neural Network Modeling

A Flexible Multifunctional PAN Piezoelectric Fiber with Hydrophobicity, Energy Storage, and Fluorescence.

Lightweight, flexible, and hydrophobic multifunctional piezoelectric sensors have increasingly important research value in contemporary society. They can generate electrical signals under the action of pressure and can be applied in various complex scenarios. In this study, we prepared a polyacrylonitrile (PAN) composite fiber doped with imidazolium type ionic liquids (ILs) and europium nitrate hexahydrate (Eu (NO3)3·6H2O) by a facile method. The results show that the PAN composite fibers had excellent mechanical properties (the elongation at break was 114% and the elastic modulus was 2.98 MPa), hydrophobic self-cleaning ability (water contact angle reached 127.99°), and can also emit light under UV light irradiation red fluorescence. In addition, thanks to the induction of the piezoelectric phase of PAN by the dual fillers, the composite fibers exhibited efficient energy storage capacity and excellent sensitivity. The energy density of PAN@Eu-6ILs reached a maximum of 44.02 mJ/cm3 and had an energy storage efficiency of 80%. More importantly, under low pressure detection, the sensitivity of the composite fiber was 0.69 kPa-1. The research results show that this PAN composite fiber has the potential to act as wearable piezoelectric devices, energy storage devices, and other electronic devices.

Tunable Microwave Flow System for Scalable Synthesis of Alkyl Imidazolium-type Ionic Liquids

Tunable Microwave Flow System for Scalable Synthesis of Alkyl Imidazolium-type Ionic Liquids

Integrated Bending Actuation and the Self‐Sensing Capability of Poly(Vinyl Chloride) Gels with Ionic Liquids

AbstractSoft actuation materials often only perform an actuation function, and do not achieve the function of self‐sensing. In this work, the polyvinyl chloride (PVC) gels are prepared with a plasticizer of dibutyl adipate (DBA) and small amount of imidazolium type ionic liquids (ILs), and are demonstrated that the PVC/DBA/ILs gels deliver the integrated bending actuation and capacitance pressure self‐sensing capability. The bending actuation performances and sensing behavior of PVC/DBA/ILs are related to the migrability of movable ions from ILs, which are dependent on the dissociation of anions and cations of ILs, and the concentration of ILs. Among the ILs, the PVC/DBA gel with 3.3 wt% 1‐allyl‐3‐methylimidazolium bis ((trifluoromethyl)sulphonyl) imide (P/[AMIM]NTF2 (3.3 wt%)) exhibits best bending displacement of 6.6 mm (corresponding to 24° of bending angle) at 7.2 kV (180 V mm−1 of nominal electric field). In addition, the P/[AMIM]NTF2 (3.3 wt%) exhibits 0.42 kPa–1 capacitance pressure sensitive in the pressure range 0 to 2.2 kPa, and a sudden change in capacitance in the pressure range 2.2–2.7 kPa with 47.5 kPa–1 of sensitivity. The results can provide a new idea for developing integrated sensing and actuation functions of electroactive dielectric polymer gels.

Investigating the Proton and Ion Transfer Properties of Supported Ionic Liquid Membranes Prepared for Bioelectrochemical Applications Using Hydrophobic Imidazolium-Type Ionic Liquids.

Hydrophobic ionic liquids (IL) may offer a special electrolyte in the form of supported ionic liquid membranes (SILM) for microbial fuel cells (MFC) due to their advantageous mass transfer characteristics. In this work, the proton and ion transfer properties of SILMs made with IL containing imidazolium cation and [PF6]− and [NTf2]− anions were studied and compared to Nafion. It resulted that both ILs show better proton mass transfer and diffusion coefficient than Nafion. The data implied the presence of water microclusters permeating through [hmim][PF6]-SILM to assist the proton transfer. This mechanism could not be assumed in the case of [NTf2]− containing IL. Ion transport numbers of K+, Na+, and H+ showed that the IL with [PF6]− anion could be beneficial in terms of reducing ion transfer losses in MFCs. Moreover, the conductivity of [bmim][PF6]-SILM at low electrolyte concentration (such as in MFCs) was comparable to Nafion.

Imidazolium-type ionic liquid-assisted formation of the MFI zeolite loaded with metal nanoparticles for hydrogenation reactions

Zeolites loaded with metal nanoparticles (NPs) stand out for their distinct activity and selectivity as heterogeneous catalysts. However, the poor stability of metal species limits their applications. Herein, we report a novel synthetic strategy for stabilizing metal nanoparticles inside the MFI zeolite. For the first time, alkoxysilane functional imidazolium-type ionic liquids (ImILs) were used as assistant agents to protect metal precursors (Pt and Pd) against precipitation during the hydrothermal synthesis of the MFI zeolite. The positively charged imidazolium groups in ImILs interact with the negatively charged metal precursors (PtCl42−, PdCl42−etc.), while the alkoxysilane groups participate in zeolite crystallization. Scanning transmission electron microscopy images indicate that most of the Pt and Pd nanoparticles (average diameters of approximately 1.0 nm and 1.7 nm, respectively) are confined in channels or intersections of the MFI zeolite. The shape-selectivity effect on nitroarene hydrogenation over Pt@MFI_ImILs confirmed the successful encapsulation of metal NPs into the MFI matrix. The conversion of the small molecule 4-nitrotoluene is >99%, whereas the bulky 1,3-dimethyl-5-nitrobenzene shows 5.8% conversion. Simultaneously, the Pd@MFI_ImILs catalyst affords a higher reaction rate (25 mmol/s/gMe) than the impregnated Pd@MFI_Imp catalyst (9 mmol/s/gMe) in propene hydrogenation, which is ascribed to the uniform distribution of Pd nanoparticles. The ImIL-assisted synthesis strategy can be therefore successfully used to confine small metal nanoparticles in the MFI zeolite while maintaining its high catalytic activity and shape-selectivity.

Study on the properties of density, viscosity, excess molar volume, and viscosity deviation of [C2mim][NTf2], [C2mmim][NTf2], [C4mim][NTf2], and [C4mmim][NTf2] with PC binary mixtures

The imidazolium type ionic liquids (ILs) 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ([C2mim][NTf2] and [C4mim][NTf2]) were synthesized. For comparing, the ILs with introduction of methyl group 1-alkyl-2,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2mmim][NTf2] and [C4mmim][NTf2]) were also prepared. The density and viscosity of the systems composed of above ILs and propylene carbonate (PC) were determined. The determined uncertainties are u(ρ) = 0.00010 g·cm−3 for density and ur(η) = 0.02 for viscosity, respectively. The excess molar volumes, thermal expansion coefficients, viscosity deviations, and a-constant were calculated. According to Redlich−Kister equation, the relationship between excess molar volume, viscosity deviation and mole fraction was fitted. By comparing with the systems of the same ILs in other organic solvents, the above-mentioned properties were discussed and the influence of introduced methylene group and methyl group on the above properties was analyzed.

Viscosity and relative viscosity of hydrophobic imidazolium type ionic liquids with dimethyl carbonate

The viscosity of four dilution solution systems was determined for ionic liquids (ILs) with Dimethyl Carbonate (DMC) at lower concentration from 288.15 K to 313.15 K. The ILs include 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2mim][NTf2]), 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C4mim][NTf2]), 1-ethyl-2,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2mmim][NTf2]), and 1-butyl-2,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C4mmim][NTf2]). The viscosities of systems have been discussed at studied concentration from 288.15 to 313.15 K. The temperature dependence on viscosities was fitted according to the Vogel-Fulcher-Tammann equation. The activation energies for viscous flow have been obtained from Arrhenius equation at different concentration range. The relative viscosities (ηr) were also calculated and analyzed according to the Jones–Dole equation at different molar concentration ranges. The slopes of the parameter, B-coefficient/dm3·mol−1, dependence on temperature, T/K have also been discussed according to the methyl and methylene groups introduction. The effects of methyl or methylene group introduction on ILs cation have also been discussed to solute–solute or solute–solvent interactions.

Apparent molar volumes of hydrophobic imidazolium type ionic liquids with dimethyl carbonate

The density of four ionic liquids 1-alkyl-2-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2mim][NTf2] and [C4mim][NTf2]), 1-alkyl-2, 3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2mmim][NTf2] and [C4mmim][NTf2]) have been determined with Dimethyl Carbonate (DMC) at lower concentration from 288.15 to 313.15 K at atmospheric pressure. Apparent molar volumes, Vϕ/m3·mol−1, have been calculated from the experimental densities. The effects of the methyl or methylene groups of the imidazolium cation on the above properties are discussed in deeply. The infinite dilution apparent molar volumes, Vϕ0/m3·mol−1 can be obtained from apparent molar volumes according to a Redlich-Rosenfeld-Meyer equation. The limiting apparent molar expansibility, Eϕ0/cm3·mol−1·K−1, have been calculated by the parameters from Redlich-Rosenfeld-Meyer equation. The thermal expansion coefficient, α/K−1, has also been calculated in the studied concentration range.

Aggregation-induced emission-based ionic liquids for bacterial killing, imaging, cell labeling, and bacterial detection in blood cells

A series of aggregation-induced emission (AIE)-based imidazolium-type ionic liquids (ILs) were designed and synthesized for bacterial killing and imaging, cell labeling, and bacterial detection in blood cells. The AIE-based ILs showed antibacterial activities against both Escherichia coli and Staphylococcus aureus. The carbon chain length of substitution at the N3 position of the imidazolium cations highly affects the antibacterial properties of ILs. Owing to their AIE characteristics, the ILs could selectively capture fluorescence image of dead bacteria while killing the bacteria. The fluorescence intensity varied with the concentration of bacteria, indicating that AIE-based ILs has potential as an antibacterial material and an efficient probe for bacterial viability assay. In addition, the synthesized AIE-based ILs exhibit relatively low cytotoxicity and hemolysis rate and therefore potential for cell labeling, as well as bacterial detection in blood cells. Statement of SignificanceBacteria are ubiquitous, especially the pathogenic bacteria, which pose a serious threat to human health. There is an urgent need for materials with efficient antibacterial properties and biocompatibility and without causing drug resistance. In this work, we synthesized a series of aggregation-induced emission (AIE)-doped imidazolium type ionic liquids (ILs) with multifunction potential of bacterial killing and imaging, cell labeling, and detection of bacteria from blood cells. The synthesized AIE-based ILs can image dead bacteria at the same time of killing these bacteria, which can avoid the fluorescent dyeing process. Simultaneously, the fluorescent imaging of dead bacteria can be distinguished by the naked eye, and the fluorescence intensity from the AIE-based ILs varied with the concentration of bacteria. In addition, the AIE-based ILs exhibit relatively low cytotoxicity and hemolysis rate and therefore potential for cell labeling as well as detection of bacteria from red blood cell suspension.

Aggregation-Induced Emission-Based Ionic Liquids for Bacterial Killing, Imaging, Cell Labelling and Bacterial Detection in Blood Cells

A series of aggregation-induced emission (AIE)-based imidazolium type ionic liquids (ILs) were designed and synthesized for bacterial killing and imaging, cell labelling and bacterial detection in blood cells. The AIE-based ILs showed antibacterial activities against both E. coli and S. aureus. The carbon chain length of substitution at the N3 position of the imidazolium cations highly affect the antibacterial properties of ILs. Due to their AIE characteristics, the ILs could selectively fluorescent image dead bacteria while killing the bacteria. The fluorescence intensity varied with the concentration of bacteria, indicating that the AIE-based ILs would be an excellent antibacterial material as well as an efficient probe for bacterial viability assay. In addition, the synthesized AIE-based ILs exhibit relatively low cytotoxicity and hemolysis rate, and therefore potential for cell labelling, as well as bacterial detection in blood cells.

Selection rules for estimating the solubility of C4-hydrocarbons in imidazolium ionic liquids determined by machine-learning tools

Solubilities of C4-hydrocarbons, 1,3-butadiene (13BD), trans/cis-2-butene (T2B and C2B), 1-butene (1B), isobutene (i-But), isobutane (i-B), and butane (B), in 3267 different imidazolium-type ionic liquids (ILs) in a temperature range from 273.15 to 373.15 K were estimated by means of the COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) calculations. Simple temperature-dependent mathematical expressions were developed to predict the solubility of 13BD, C2B, T2B, 1B, i-But, i-B, and B at any temperature in a range from 273 to 373 K. The COSMO-RS results for each hydrocarbon considered were then analyzed using machine learning tools, including association rule mining and decision tree classification, using semi-empirically derived molecular descriptors of ILs. It was found that the polarizabilities of both cation and anion, together with the anion's CPK (space filling model) area, are the most important descriptors for determining the affinity of ILs towards C4-hydrocarbons. Results also present the selection rules for imidazolium ILs, offering opportunities for the rational design of new ILs by using these simply-determined structural descriptors to meet the desired solubility (or selectivity) requirements for each C4-hydrocarbon considered.

Crystal Forms and Microphase Structures of Poly(vinylidene fluoride-co-hexafluoropropylene) Physically and Chemically Incorporated with Ionic Liquids

The effects of incorporating two imidazolium-type ionic liquids (ILs), 1-vinyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide (IL-TFSI) and 1-vinyl-3-butylimidazolium chloride (IL-Cl), on the crystal forms and phase microstructures of poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-co-HFP), were investigated. No change in the crystal form was observed with the incorporation of IL-TFSI because of the selective interaction between the IL and HFP moieties of the P(VDF-co-HFP) molecular chains. In contrast, the incorporation of IL-Cl induces an α-to-β crystal form transition because of the interactions between IL-Cl and the VDF moieties. Furthermore, the incorporation of IL-TFSI led to distinct phase separation of P(VDF-co-HFP), whereas a homogeneous phase structure was maintained with the incorporation of IL-Cl. Element mapping images reveal that the specific interactions of IL-TFSI with the HFP moieties induce enrichment of the HFP moieties, which results in well-defined HFP/IL-TFSI nanodomain...

Redox-responsive ferrocene-containing poly(ionic liquid)s for antibacterial applications

Ferrocene (Fc)-containing imidazolium type ionic liquids (ILs) and corresponding poly(ionic liquid) (PIL) membranes with tunable antibacterial activity based on electrochemical redox reaction and host-guest chemistry were developed. The effect of Fc moiety on the antimicrobial activities against both Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ) was studied by minimum inhibitory concentration (MIC). The presence of Fc groups highly enhanced the antibacterial efficiency of Fc-containing ILs because of the generation of reactive oxygen species (ROS). The electrochemical oxidation of Fc to Fc+ and the formation of inclusion complexes between Fc and β-CD via host-guest interactions decreased the antibacterial activities of ILs and PIL membranes. The antibacterial activities may be recovered in some extent upon the electrochemical reduction of Fc+ to Fc or the exclusion of the Fc out of the cavity of β-CD. Furthermore, all the Fc-containing PIL membranes showed relatively low hemolysis activities and none cytotoxicity toward human cells, indicating clinical feasibility in topical applications.

Assessment via the modified gompertz-model reveals new insights concerning the effects of ionic liquids on biohydrogen production

Lignocellulosic biofuel, in particular hydrogen gas production is governed by successful feedstock pretreatment, hydrolysis and fermentation. In these days, remarkable attention is paid to the use of ionic liquids to make the fermentable regions of lignocellulose biomass more accessible to the biocatalysts. Although these compounds have great potential for this purpose, their presence during the consecutive fermentation stage may pose a threat on process stability due to certain toxic effects. This, however, has not been specifically elaborated for dark fermentative biohydrogen generation. Hence, in this work, two common imidazolium-type ionic liquids (1-butyl-3-methylimidazolium acetate, ([bmim][Ac]) and 1-butyl-3-methylimidazolium chloride, ([bmim][Cl])) were employed in mixed culture biohydrogen fermentation to investigate the possible impacts related to their presence and concentrations. The batch assays were evaluated comparatively via the modified Gompertz-model based on the important parameters characterizing the process, namely the biohydrogen production potential, maximum biohydrogen production rate and lag-phase time.

Reversible surface activity and self-assembly behavior and transformation of amphiphilic ionic liquids in water induced by a pillar[5]arene-based host-guest interaction

In this paper, we aimed to develop a reversible and effective method to control the surface activity and self-assembled morphology of amphiphilic imidazolium-type ionic liquids (G) in water. For this purpose, a series of pillar[5]arene/imidazolium supramolecular complexes were designed and prepared. Before the formation of the host-guest complex, the surface activity of G7 worked well, and foams could be generated easily. However, after the addition of water-soluble pillar[5]arene (WP5), the rigid WP5 platform caused steric hindrance that prevented the hydrophobic chains on G7 from getting close to each other, inducing the change in surface activity. On the other hand, because paraquat (PQ) has a larger association constant with WP5 than G7, the surface activity of the solution can be recovered after the addition of PQ. TEM confirmed that self-assembled morphologies of this reversible system transformed from nanoparticles to nanosheets then to nanoparticles. It is anticipated that this supramolecular method for controlling the surface activity of amphiphiles in a reversible way may find application in fields where fast foaming and defoaming are needed.

Recent advances in metal extraction improvement: Mixture systems consisting of ionic liquid and molecular extractant

Abstract Ionic liquids (ILs), also termed “green” and “designer” solvents, have been proposed as promising solvents for diverse applications. This review focused on the improvements brought about by mixing ILs with molecular extractants (MEs) in solvent extraction processes for metal extraction and separation. Mixture systems consisting of IL with ME were collected and discussed on the basis of the functional cations of ILs, such as ammonium-type, phosphonium-type and imidazolium-type ILs. IL was found to play a role as an active component by generating a new acid/base coupling bi-functional ionic liquid (ABC-BIL) or as a diluent when combined with acidic or neutral ME in IL-ME mixture systems. The merits and drawbacks of IL-ME systems were reviewed and compared with conventional ME systems alone in terms of the preparation route, separation behavior and extraction mechanism. Further approaches to the improvement of IL-ME systems, such as extraction enhancement, stripping and regeneration, were discussed. The summaries and comparisons made in the present review may indicate future directions for the development and application of ILs in metal solvent extraction technology.

Methimazolium-based ionic liquid crystals: Emergence of mesomorphic properties via a sulfur motif

We describe the proficient synthesis and thermotropic mesomorphicity of thioether–functionalized imidazolium–type ionic liquids containing C12 and C18 chains associated with Br− and OTf− anions. The mesomorphic behavior and phase transition temperatures were studied by Polarizing Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and Small-Angle X-ray Scattering (SAXS). The ionic liquids with bromide anion display Smectic A lamellar phase giving homeotropic and fan-shaped textures. The layered crystallographic structure is reported by Single-Crystal XRD. The electrochemical characteristics of the ionic liquids with C18 side chain have been determined via Cyclic Voltammetry.

On the efficiency of dual-chamber biocatalytic electrochemical cells applying membrane separators prepared with imidazolium-type ionic liquids containing [NTf2]− and [PF6]− anions

In this study, the dependency of energy recovery on separator characteristics applied in microbial fuel cells (MFCs) was sought by testing an emerging class of membranes (supported ionic liquid membranes (SILMs), prepared with [hmim][PF6] and [bmim][NTf2] ionic liquids) comparatively with well-known proton exchange (Nafion N115) and microfiltration (PVDF) counterparts. Crucial membrane features such as O2 and substrate (acetate as the sole carbon source) crossovers were assessed and as a result, mass transfer as well as diffusivity coefficients of these compounds (kO, kA, DO, DA, respectively) were determined. The experiments showed that SILM-operated MFCs could work in a reliable way and among them, the [bmim][NTf2]-based one produced higher specific energy yield (YS=9.78kJg−1CODinm−2) than the Nafion-MFC (YS=8.25kJg−1CODinm−2) used as an important reference. This outcome was found to be associated with the membrane-cross oxygen shuttle properties of the membranes (kO=1.25cms−1 and 1.31cms−1, respectively). As for the two SILMs, significant differences in terms of the energy yield, mass transfer and diffusion coefficients were noted, however, it has appeared from cell polarization measurements that the internal resistances of the SILM-MFCs were nearly the same. The evaluation of the SILM-operated MFCs’ power production was complemented by measuring the dielectric traits of ionic liquids that can be related with the ion conductivity of these materials. It turned out that the [hmim][PF6] IL had an order of magnitude lower ionic conductivity.