Specific Ionic Liquids Research Articles

Rheology characterization of ionic liquids under high pressure and high temperature

Ionic liquids (ILs) are liquid salts that exist at or below ambient temperatures and are composed of ion pairs. They offer promising alternatives to toxic, hazardous, highly flammable, and volatile solvents in various applications such as solution preparation, dispersion, gel formation, composites, and polymer melts. ILs possess unique and interesting characteristics, including excellent chemical and thermal stability and low vapor pressures. Understanding the rheological properties of ILs is essential to optimizing IL performance. This paper presents a comparative analysis of the rheological properties of two ionic liquids, NHexylpyridinium tetrafluoroborate (HPyBF4) and NHexylpyridinium bromide (HPyBr), under different shear rates, temperatures, and pressures. Rheological measurements were performed under varying controlled pressure and temperature conditions. The experimental investigation covered a pressure range of 689–12,411 kPa [100–1800 psi] and a temperature range from room temperature up to 522 kelvin (K) [480°F]. The primary objective is to explore and compare the flow behavior and viscoelastic characteristics of HPyBF4 and HPyBr under high-pressure and high-temperature conditions. The experimental data showed that HPyBF4 and HPyBr exhibited shear-thinning behavior, and pressure had an insignificant effect on rheology compared to the temperature effect. Under the same testing conditions, HPyBr showed higher shear stress and viscosity than HPyBF4. This research significantly contributes to the improved understanding of the rheological behavior of these specific ionic liquids and their suitability for diverse industrial and scientific applications, particularly in high-pressure and high-temperature environments.

Study on the interaction properties of ionic liquid mixtures with a common anion: A combination of spectral and theoretical study

Ionic liquid mixtures have garnered significant attention due to their promising applications. Despite this interest, there remains a limited understanding of these mixtures, particularly regarding their microstructure. A comprehensive understanding of their microstructural characteristics and properties is essential for harnessing the full potential of ionic liquid mixtures. In this work, the structural properties and interactions were investigated within mixtures of two specific ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4C1im][NTf2]) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4C1pyrr][NTf2]). Employing a combination of experimental and theoretical methods, the following conclusions were obtained: (1) The cis- and trans-configurations of [NTf2]− coexist in pure ionic liquids and their mixtures; (2) The primary interaction site of [C4C1im]+ and [C4C1pyrr]+ are C2−H and H on the methylene group attached to the N atom, respectively. It mainly interacts with O atoms in [NTf2]− anions through hydrogen bond interactions; (3) The introduction of [C4C1pyrr][NTf2] weakens the hydrogen bonding interactions within the ionic liquid mixtures.

A ciprofloxacin derived task specific ionic liquid as a highly selective extractant of thorium versus uranium

Highly selective extraction of thorium versus uranium using a TSIL system.

Fully Bio-Based Ionic Liquids for Green Chemical Modification of Cellulose in the Activated-State.

Biopolymers, especially cellulose, are vital to transitioning to a circular economy and reducing our reliance on fossil fuels. However, for many applications a high degree of cellulose hydroxyl modification is necessary. The challenge is that the chemical features of the hydroxyls of cellulose and water are similar. Therefore, chemical modification of cellulose is often explored under non-aqueous conditions with systems that result in high hydroxyl accessibility and reduce cellulose aggregation. Unfortunately, these systems depend on hazardous and complex solvents from fossil resources, which diverge from the initial sustainability objectives. To address this, we developed three new betaine-based ionic liquids that are fully bio-based, scalable, and green. We found that a specific ionic liquid had the perfect chemical features for the chemical activation of cellulose without disturbing its crystalline ordering. The high activation in heterogeneous conditions was exemplified by reacting cellulose with succinic anhydride, resulting in more than 30 % conversion of all hydroxyls on cellulose. Overall, this work opens new perspectives for the derivatization of cellulosic materials while simultaneously "keeping it green".

Towards Understanding the Variation of Electrode Design Parameters on the Electrochemical Performance of Aluminum Graphite Batteries: An Experimental and Simulation Study

AbstractDue to their high power density and availability, aluminum batteries consisting of graphite positive electrode and ionic liquid electrolytes are promising candidates for post‐lithium‐ion batteries. However, the effect of the various electrode design parameters on their electrochemical performance is not well understood. Herein, a high‐fidelity physics‐based model validated with experimental data obtained from a Swagelok cell consisting of an aluminum metal negative electrode, imidazolium ionic liquid electrolyte, and graphite positive electrode is used to study the effects of various electrode design parameters on the discharge capacity. The model is used to optimize the design of the electrodes by generating several Ragone plots, estimating the optimum current density for a given cell design, and explaining the limitations of the cells based on the transport of the electroactive species. An optimum graphite thickness of 50 μm is obtained for all the discharge times considered in this study. Determining the ideal electrode configuration for Al‐graphite batteries using different ionic liquid electrolytes and considering various discharge durations could provide a reference point for evaluating the suitability of a specific ionic liquid electrolyte in a particular use case.

Novel electrolytes based on mixtures of dimethyl sulfoxide task specific zwitterionic ionic liquid and lithium salts: Synthesis and conductivity studies

Novel methyl sulfoxide imidazolium-based zwitterionic low melting salts was synthesized and characterized. The combination of this functionalized zwitterion and lithium bis(trifluoromethylsulfonyl)amide (LiNTf2) salts at different molar ratios of render to low melting mixtures, which can exhibit an ionic conductivity as high as 3.4 × 10−5 S cm−1 at 30 °C or 2.9 × 10−3 S cm−1 at 120 °C and a high thermal decomposition temperature higher than 250 °C. The thermal activation energy shown two clearly different Arrhenius trend. For all the mixtures the temperature where the slope of the Arrhenius plot changes is on the range of the melting temperature experimentally observed for the mixture. Below the melting temperature, the values of activation energy are around of two times higher than the values observed for all the mixtures above the melting temperature. On the other hand, in all the mixtures, we have observed that conductivity increases monotonically on the composition of the mixture. These non-volatile and highly polar novel materials can be used for the development of devices targeting high ionic Li-ion conductivity.

Porous liquid metal-organic frameworks with selectively high gas solubility

Porous liquid metal–organic frameworks (MOFs) have recently been discovered rather promising for gas absorption and separation in practical chemical industry processes. In this work, we successfully fabricated a kind of MOF-based porous liquid (i.e., UIO-66-PL) by dispersing the hydrophilic porous filler of UIO-66-NH2 nanoparticles into a specific hydrophilic ionic liquid (IL, [HEMIM][DCA]) through the wet-impregnation method. The obtained UIO-66-PL was a kind of stable porous liquid with well-maintained permanent porosity and liquid-like behavior at room temperature. More importantly, this UIO-66-PL has larger gas absorption capacities than its reference IL hindered solvent as the well-preserved permanent porosity could act as free void space for gas accommodation. Also, IL could serve as a selective gate for target gas to the permanent porosity within UIO-66-PL, i.e., the majority of the permanent porosity in UIO-66-PL is inaccessible to nitrogen, but available for carbon dioxide, demonstrating that this UIO-66-PL could function as a type of fluid selective gas sorbent with high target gas solubility.

Ion-Mediated Protein Stabilization on Nanoscopic Surfaces.

The emergence of nanoparticles in biomedical applications has made their interactions with proteins inevitable. Nanoparticles conjugated with proteins and peptide-based constructs form an integral part of nanotherapeutics and have recently shown promise in treating a myriad of diseases. The proper functioning of proteins is critical to achieve their biological functions. However, interface issues result in the denaturation of proteins, and the loss of orientation and steric hindrance can adversely affect the function of the conjugate. Furthermore, surface-induced denaturation also triggers protein aggregation, resulting in amyloid-like species. Understanding the mechanistic underpinnings of protein-nanoparticle interactions and controlling their interfacial characteristics are critical and challenging due to the complex nature of the conjugates. In this milieu, we demonstrate that ionic liquids can be suitable candidates for stabilizing protein-nanoparticle interactions by virtue of their excellent protein-preserving properties. We also probe the previously unexplored mechanism of ion-mediated stabilization of the protein molecules on the nanoparticle surface. The protein-nanoparticle conjugates consist of lysozyme and choline-based ionic liquids characterized by optical and electron microscopy techniques combined with surface-sensitive plasmon-enhanced Raman spectroscopy. Furthermore, atomistic molecular dynamics simulations of the conjugates delineate interfacial interactions of the protein molecules and the modulation by the ions, particularly the conformational changes and the dynamic correlation when the protein and specific ionic liquid molecules are adsorbed on the nanoparticle surface. The combined experimental and computational studies showed the synergistic behavior of the ions of the ionic liquids, specifically the orientation and coverage of the anions aided by the cations to control the surface interactions and hence the overall protein stability. These studies pave the way for using ionic liquids, particularly their biocompatible counterparts in nanoparticle-based complexes, as stabilizing agents for biomedical applications.

Structural elucidation of polydopamine facilitated by ionic liquid solvation.

Minimal understanding of the formation mechanism and structure of polydopamine (pDA) and its natural analogue, eumelanin, impedes the practical application of these versatile polymers and limits our knowledge of the origin of melanoma. The lack of conclusive structural evidence stems from the insolubility of these materials, which has spawned significantly diverse suggestions of pDA's structure in the literature. We discovered that pDA is soluble in certain ionic liquids. Using these ionic liquids (ILs) as solvents, we present an experimental methodology to solvate pDA, enabling us to identify pDA's chemical structure. The resolved pDA structure consists of self-assembled supramolecular aggregates that contribute to the increasing complexity of the polymer. The underlying molecular energetics of pDA solvation and a macroscopic picture of the disruption of the aggregates using IL solvents have been investigated, along with studies of the aggregation mechanism in water.

Newly synthesized imidazolium precursors for CO2utilization and sequestration: aproticversusprotic salts

This work describes the one-pot synthesis for 1,3-bis(3-(1,3-dioxoisoindolin-2-yl)propyl)-1H-imidazol-3-ium bromide, and other protic and aprotic derivatives.

The Electrical Conductivity of Ionic Liquids: Numerical and Analytical Machine Learning Approaches

In this paper, we incorporate experimental measurements from high-quality databases to construct a machine learning model that is capable of reproducing and predicting the properties of ionic liquids, such as electrical conductivity. Empirical relations traditionally determine the electrical conductivity with the temperature as the main component, and investigations only focus on specific ionic liquids every time. In addition to this, our proposed method takes into account environmental conditions, such as temperature and pressure, and supports generalization by further considering the liquid atomic weight in the prediction procedure. The electrical conductivity parameter is extracted through both numerical machine learning methods and symbolic regression, which provides an analytical equation with the aid of genetic programming techniques. The suggested platform is capable of providing either a fast, numerical prediction mechanism or an analytical expression, both purely data-driven, that can be generalized and exploited in similar property prediction projects, overcoming expensive experimental procedures and computationally intensive molecular simulations.

Solubility of CO2 in Ionic Liquids with Additional Water and Methanol: Modeling with PC-SAFT Equation of State

The superior properties of specific ionic liquids (ILs), such as negligible volatility, high thermal stability, flexible designability, and their affinity to capture CO2, make them an attractive alternative to chemical and physical solvents that are currently used in CO2 capture processes. However, a limitation to use ILs for industrial CO2 capture is their high viscosity compared to conventional solvents, which leads to a lower CO2 capture rate and higher pumping cost. The viscosity of ILs can be reduced by adding a co-solvent, such as water or methanol. In this work, solubility, vapor–liquid equilibria (VLE), and liquid–liquid equilibria (LLE) for binary and ternary mixtures involving CO2, ILs, water, and methanol have been systematically investigated by employing perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state with two different strategies. ILs were considered as self-associating chain molecules with two association sites in the first strategy. As a comparison, they were regarded as strong electrolytes that dissociate into anions and cations in the second strategy. It was found that both strategies provide accurate correlations in modeling CO2 solubilities in ILs and LLE of binary ILs/water systems. Four ternary systems were selected to verify the predictive capability of the two strategies. For water-containing systems, both strategies performed excellently when binary interaction parameters (BIPs) can be obtained by fitting to experimental data, while they performed poorly for system with few experimental data. For cases where methanol acted as a co-solvent, accurate predictions were obtained with both strategies, even without any BIPs. PC-SAFT was found to be a potential practical tool to develop CO2 capture processes with new alternative solvents when there are sufficient experimental data for binary mixtures.

Exploring of spacer fluorination effect on the characteristics and physicochemical properties of the newly designed task specific dicationic imidazolium-based ionic liquids: A quantum chemical approach

Forming possibility of two series of DILs based on the 1,4-bis(4-methyl-imidazolium) p-phenyl ([p-C6H4(MIM)2]2+ = [PHIM]2+) and 1,4-bis (4-methyl- imidazolium) p-1,1′-perfluoro- phenyl ([p-C6F4(MIM)2]2+= [PFIM]2+) dications and [Y1]− = [CH3CO2]−, [Y2]− = [NO3]−, [Y3]− = [CF3CO2]−, [Y4]− = [BF4]−, [Y5]− = [ClO4]− and [Y6]− = [PF6]− anions were explored using quantum computational methods. The roles of anion exchange as well as fluorination of the spacer group (phenyl ring) on the physicochemical properties of the designed DILs ([PHIM][Y1-6]2 and [PFIM][Y1-6]2) were evaluated. The potential electrostatic curves, values of interaction thermodynamic energies, structural parameters, topological properties, natural charge of atoms, charge transfer (CT) and charge transfer energy (E(2)) of acceptor-donor interactions, reduced gradient density (RGD) plots, and electrochemical windows (ECW) were examined. The obtained corrected interaction energies for [PHIM][Y1-6]2 DIL series are ranging from -256.44 to -214.83 kcal mol−1 and those are for [PFIM][Y1-6]2 DILs are ranging from -265.12 to -221.85 kcal mol−1. The results indicate that the DILs based on CH3CO2−, NO3− and CF3CO2− anions form stronger hydrogen bonds with the dications. The strength of the interactions between ionic constructing parts in [PFIM][Y1-6]2 DILs are about 6.04 -10.28 kcal mol−1 more than the [PHIM][Y2-6]2 DILs analogues. Nature of the hydrogen bond interactions between ionic parts in most of the [PHIM][Y1,2]2 and [PFIM][Y1-3]2 DILs determined as electrostatic interaction. The order of changes in some macroscopic properties such as melting point, critical temperature, enthalpy of vaporization, electrical conductivity, viscosity and electrochemical stability of the studied DILs were estimated stand on the calculated intermolecular interaction energies. Results showed, DILs that their cathodic and anodic stability controlled by their corresponding dications (such as: [PHIM][Y4,6]2 and [PFIM][Y4,6]2), have higher ECW values in comparison to the others.

A carbon nanosphere nanofluid for improving the toughness and thermal properties of epoxy composites

A carbon nanosphere nanofluid (CNS-nanofluid) was successfully prepared through the non-covalent modification of carbon nanosphere (CNS) with the specific ionic liquid (i.e. [M2070][VBS]) at first. The resulting CNS-nanofluid is a homogeneous and stable fluid with liquid-like behaviour at room temperature, and which shows better dispersion stability in its good solvents and improved processability than the pristine CNS. Subsequently, this CNS-nanofluid was used as a kind of novel functional filler and incorporated into epoxy matrix to prepare the CNS-nanofluid filled epoxy composites (CNS-nanofluid/EP composites). The toughness and thermal properties of those CNS-nanofluid/EP composites were carefully characterized and analysed. And it was found that this CNS-nanofluid could respectively improve the impact toughness and glass transition temperature of the CNS-nanofluid/EP composites to 19.8 kJ m−2 and 122.5 °C at the optimum amount, demonstrating that this CNS-nanofluid is a kind of promising functional filler to achieve robust epoxy composites, and thus opening up new possibilities with great significance for epoxy composites in high-performance applications.

Selective extraction of heavy metals (Fe, Co, Ni) from their aqueous mixtures by Task-Specific salicylate functionalized imidazolium based ionic liquid

Iron (Fe), cobalt (Co) and nickel (Ni) together are known as the iron triad exhibiting similar chemical and physical affinities in the periodic table. We have developed a green, efficient, highly selective, environmentally benign, water-IL biphasic solvent extraction system for the selective extraction of iron triad elements from their aqueous mixtures at room temperature using a new salicylate functionalized imidazolium based task specific ionic liquid (TSIL) i.e. 1,3-dioctylimidazolium 2-hydroxybenzoate [DOIM][OHB]. Co2+ was extracted within 5 min as a blue complex while the residual mixture was allowed to stand overnight. In the meantime, Fe2+ was oxidized to Fe3+ without using any additional oxidants and was extracted as a red coloured complex. Ni2+ was not observed visibly, however atomic absorption spectroscopy (AAS) indicated the presence of less than 1% Ni2+. The extraction of heavy metal ions follows neutral extraction mechanism elucidated through UV visible spectroscopy.

Enhancement of post-combustion CO2 capture capacity by incorporation of task-specific ionic liquid into ZIF-8

In this present work, two task specific ionic liquids (TSILs) were encapsulated into the framework of a Zeolite imidazolate framework-8 (ZIF-8) to enhance its CO2 capture capacity and CO2/N2 selectivity at post-combustion conditions. 1-Ethyl-3-methylimidazolium amino-acetate {[EMIM][glycine (Gly)]} and 1-Ethyl-3-methylimidazolium (S)-2-aminopropionate {[EMIM][alanine (Ala)]} were selected as TSILs. [email protected] composites sorbents were prepared by varying the loading of TSIL, and properties such as sorbent thermal stability, porous structure and crystal nature of the composite were investigated. Incorporation of TSIL into ZIF-8 led to a dramatic rise in CO2 uptake particularly at pressures lower than 1.0 bar. At this low-pressure range, CO2 uptake was greater than in pristine ZIF-8 for all TSIL loadings and [email protected] composites with 30 wt% [Emim][Gly] reached a CO2 uptake capacity of 0.76 mmol·g−1 solid at 0.1 bar, and 0.88 mmol/g-solid at 0.2 bar at 303 K. These values were 13 and 7 times higher that CO2 uptake in pristine ZIF-8 at identical conditions. TSIL functionalized composites also exhibited much higher selectivity than pristine ZIF-8 at all pressures. For instance, at 30 wt% [EMIM][Gly] loading, CO2/N2 ideal selectivities at 313 K were 28 and 19 at 0.1 and 0.2 bar, respectively. This synthesized composite sorbent, with significantly high CO2 uptake, better CO2/N2 selectivity at the low-pressure region (<1.0 bar), and low isosteric heat of adsorption (Qst), confirms that [email protected] composites can be potential candidates for post-combustion CO2 capture processes and opens the door for the further development of suitable [email protected] composite sorbent to be deployed in the CO2 capture process.

Green synthesis of coumarin derivatives using Brønsted acidic pyridinium based ionic liquid [MBSPy][HSO4] to control an opportunistic human and a devastating plant pathogenic fungus Macrophomina phaseolina.

An eco-friendly simple protocol has been devised for the preparation of coumarin derivatives using doubly Brønsted acidic task specific ionic liquid (TSIL) as a catalyst. Solvent-free conditions were employed for the reaction of different substituted phenols with β-ketoester in TSIL to produce corresponding substituted coumarin derivatives in good to excellent yields at ambient conditions; at room temperature and with reduced reaction times. The ionic liquid catalyst can be recycled and reused up to five times. All the synthesized coumarins were evaluated for their antifungal activities against Macrophomina phaseolina, a plant as well as an opportunistic human pathogenic fungus affecting more than 500 plant species worldwide and with no registered commercial fungicide available against it, to date. Amongst all the coumarins tested, compounds 3f and 3i showed excellent antifungal activity comparable to reference fungicide mancozeb. The current methodology provides an easy and expedient way to access the coumarin core in search of potential fungicides for sustainable agriculture.

Surface Interaction of Ionic Liquids: Stabilization of Polyethylene Terephthalate-Degrading Enzymes in Solution.

The effect of aqueous solutions of selected ionic liquids solutions on Ideonella sakaiensis PETase with bis(2-hydroxyethyl) terephthalate (BHET) substrate were studied by means of molecular dynamics simulations in order to identify the possible effect of ionic liquids on the structure and dynamics of enzymatic Polyethylene terephthalate (PET) hydrolysis. The use of specific ionic liquids can potentially enhance the enzymatic hydrolyses of PET where these ionic liquids are known to partially dissolve PET. The aqueous solution of cholinium phosphate were found to have the smallest effect of the structure of PETase, and its interaction with (BHET) as substrate was comparable to that with the pure water. Thus, the cholinium phosphate was identified as possible candidate as ionic liquid co-solvent to study the enzymatic hydrolyses of PET.

Influence of the Silica Specific Surface Area and Ionic Liquids on the Curing Characteristics and Performance of Styrene-Butadiene Rubber Composites.

In this work, we present the effect of silica’s specific surface area (180 m2·g−1 and 380 m2·g−1, respectively) on the crosslinking of styrene–butadiene rubber (SBR) composites, as well as their crosslink density and functional properties, such as thermal stability, damping behavior, resistance to thermo-oxidative aging, and tensile properties. Ionic liquids (ILs) with a bromide anion and different cations, i.e., 1-butyl-3-methylimidazolium (Bmi), 1-butyl-3-methylpyrrolidinium (Bmpyr), and 1-butyl-3-methylpiperidinium (Bmpip), were used to enhance the cure characteristics of SBR compounds and the functional properties of SBR vulcanizates. It was proven that apart from the silica’s specific surface area, the filler–polymer and filler–filler physical interactions have a significant impact on the vulcanization kinetics of silica-filled SBR composites. Additionally, the performed studies have shown that ILs positively affected the dispersion of silica’s particles and reduced their ability to form agglomerates in the elastomer matrix, which enhanced the functional properties of the SBR vulcanizates.

New ionic liquid-based polyoxadiazole electrolytes for hydrogen middle- and high-temperature fuel cells

New polyoxadiazole-based supported ionic liquid membranes were designed and elaborated for the first time to be used as a middle- and high-temperature polymer electrolyte membrane for fuel cell application. The proposed membrane molecular design combined hydroxyl-functionalized sulfonated polyoxadiazole, hydrophilic polyvinylpyrrolidone and specific protic ionic liquid, thus allowing elaboration of membranes with remarkable physical-chemical characteristics. It is found that the fine tuning of the membranes properties is possible by varying the ratio of polyoxadiazole and polyvinylpyrrolidone. The obtained membranes reveal high thermal stability in dynamic and static modes (up to 350 °C), good oxidative stability, sufficient mechanical properties (Young's modulus of 0.3–21.4 MPa and elongation at break from of 6 to 174%), high degree of ionic liquid impregnation (up to 297%), stable and relatively high conductivity (up to 1.3 mS∙cm−1) in a wide temperature range (from 40 to 120 °С) and under dry conditions. All these properties make the elaborated membranes very attractive for middle- and high-temperature fuel cell application.