15th anniversary of polymerised ionic liquids

Polymerised ionic liquids (PILs) have unique properties such as low glass transition temperature (Tg) in spite of very high charge density. Due to these advanced points, PILs have been prepared and initially evaluated as ion conductive polymers. Progress of low-Tg polyelectrolytes has been previously demonstrated with polyethers having charged end(s) as a kind of PILs. Then, imidazolium-type ionic liquids (ILs) were polymerised after introducing vinyl groups onto the imidazolium cation rings. It is reasonable that the ionic conductivity of thus prepared PILs decreased due to elevation of Tg and decrease of the number of mobile small ions. Efforts were then paid to suppress drop of ionic conductivity after polymerisation. Variety of PILs has been improved to show excellent ionic conductivity, selective ion transport, and other properties. With the progress of functional ILs, some functions were also added to PILs which cannot be realised with ordinary charged polymers. In the present mini-review, we briefly introduce history of a variety of polymerised ILs and some applications of these PILs.     

Antimicrobial polyurethane coatings based on ionic liquid quaternary ammonium compounds

The antimicrobial effect of ionic liquids (ILs) as comonomers in polyurethane surface coatings was investigated. Ionic liquid-containing coatings were prepared from a hydroxyl end-capped liquid oligoester and a triisocyanate crosslinker. Three different commercially available hydroxyl end-capped ionic liquids were covalently incorporated into the coatings in order to end up with antimicrobial polyurethane films. The ionic liquids used in this study were chosen because of their structural similarities to other antimicrobial quaternary ammonium compounds (QACs). Prepared films have been examined against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli type bacteria, and showed strong antimicrobial activity.     

Ionic liquids for acetylene and ethylene separation: Material selection and solubility investigation

Potential applications of ionic liquids (ILs) for the green separation process of acetylene in ethylene and for the storage of acetylene were investigated. To deal with this proposal, the solubilities of the unsaturated hydrocarbons in various ionic liquids were evaluated. The solubility of ethylene shows a solubility parameter-dependent behavior as indicated by the proportional relationship between the natural log value of Henry's law constant and the inverse molar volume of ILs. This correlation suggests the most important role of voids formation within IL to accommodate the solutes and the applicability of regular solution theory to model the solubility behavior. Whereas, in addition to the free-volume contribution of ILs, the solubility of acetylene is largely controlled by a specific solute–solvent interaction as a result from the association of the acidic hydrogen character in acetylene and the relative basicity of the anion. Those two different solubility behaviors result in a high absorption selectivity of acetylene over ethylene in the basic ILs. ¹H NMR experiment clearly demonstrated the presence of a substantial interaction between the acetylene and the anion of IL. Interestingly, this solute–solvent interaction is reversible as indicated by the absorption–desorption test of acetylene in [BMIM][Me₂PO₄].     

Ionic liquids as active pharmaceutical ingredients

Ionic liquids (ILs) are ionic compounds that possess a melting temperature below 100 °C. Their physical and chemical properties are attractive for various applications. Several organic materials that are now classified as ionic liquids were described as far back as the mid-19th century. The search for new and different ILs has led to the progressive development and application of three generations of ILs: 1) The focus of the first generation was mainly on their unique intrinsic physical and chemical properties, such as density, viscosity, conductivity, solubility, and high thermal and chemical stability. 2) The second generation of ILs offered the potential to tune some of these physical and chemical properties, allowing the formation of "task-specific ionic liquids" which can have application as lubricants, energetic materials (in the case of selective separation and extraction processes), and as more environmentally friendly (greener) reaction solvents, among others. 3) The third and most recent generation of ILs involve active pharmaceutical ingredients (API), which are being used to produce ILs with biological activity. Herein we summarize recent developments in the area of third-generation ionic liquids that are being used as APIs, with a particular focus on efforts to overcome current hurdles encountered by APIs. We also offer some innovative solutions in new medical treatment and delivery options.     

Physical and electrochemical characterization of ionic liquids based on quaternary phosphonium cations containing a carbon–carbon double bond

Physical and electrochemical characterizations of novel two ionic liquids based on quaternary phosphonium cations containing an unsaturated carbon–carbon bond (triethyl(4-pentenyl)phosphonium and allyltributylphosphonium cations) are presented in this report. It was found that both unsaturated phosphonium cations gave low-melting salts in combination with a bis(trifluoromethylsulfonyl)amide anion. The thermogravimetric analysis suggested that the unsaturated phosphonium ionic liquids showed higher thermal stability than those of the corresponding saturated phosphonium ILs. The unsaturated phosphonium ionic liquids also exhibited relatively low viscosity and high conductivities when compared to those of the corresponding saturated phosphonium ionic liquids. These results indicate an improving effect of introducing a carbon–carbon double bond into the phosphonium cations on both the thermal stability and the transport property. The voltammetric measurements suggested that the triethyl(4-pentenyl)phosphonium-based ionic liquid showed a high cathodic stability, enabling the deposition and dissolution of metallic lithium in the phosphonium ionic liquid system.     

离子液体在纳米ZnO材料制备中的研究进展

离子液体（ILs）具有蒸气压低、液程宽、热稳定性好、结构和性质可调节等特点, 作为反应溶剂、模板剂或结构导向剂等在纳米材料制备领域得到了广泛的应用。纳米ZnO在传感器、太阳能电池、光催化和发光二极管等领域具有广泛的应用。总结了近年来ILs在纳米ZnO材料制备中的研究进展, 重点归纳和比较了常规非质子型ILs、质子型ILs、碱性ILs和聚ILs在制备纳米ZnO中的应用,及其调控纳米ZnO形貌、尺寸和性能的作用特点, 并为今后ILs应用于金属纳米材料的制备提出了建议。     

Estimation of densities of ionic liquids using Patel–Teja equation of state and critical properties determined from group contribution method

In this paper, the Valderrama and Robles group contribution model for the critical properties is extended to the prediction of densities of ionic liquids (ILs) at varying temperatures and pressures, where the critical properties of ILs are represented by the modified Lydersen–Joback–Reid group contribution method, and the density is predicted by virtue of the Patel–Teja (PT) equation of state (EOS). The group increments for totally 47 groups with respect to the extended Group Contribution Patel–Teja (GC–PT) model were determined on the basis of experimental density data for 747 pure ILs at atmospheric pressure and ambient temperature. The group increments are suitable for both the GC–PT model and the original Valderrama and Robles model for the density prediction of ILs. The correlation accuracy in terms of overall average absolute relative deviation (AARD) is 4.4% for 918 data points of density at ambient temperature and atmospheric pressure. The applicability of the GC–PT model is justified by predicting the densities of imidazolium-, pyridinium-, and phosphonium-based ILs containing various anions over a wide range of temperatures and pressures and the vapor pressures of five alkylimidazolium-based ILs at varying temperatures, which implied the rationality of the group increments and the critical properties of ILs, as well as the potential uses of the GC–PT model for the thermodynamic modeling of IL-containing systems.     

Electrochemical studies and self diffusion coefficients in cyclic ammonium based ionic liquids with allyl substituents

Several cyclic ammonium-based ionic liquids (ILs) with allyl substituent are synthesized, these allyl substituent ILs have high ionic conductivity (up to 4.72 mS cm⁻¹ at 30 °C) and wide electrochemical window of 5 V. The electrochemical behaviors of two organometallic redox couples Fc/Fc⁺ (ferrocene/ferrocenium) and Cc/Cc⁺ (cobaltocene/cobaltocenium) have been studied in these ILs, the calculated Stokes–Einstein product (Dη T⁻¹) of ferrocene in ILs is larger than that of cobaltocenium in ILs. The self-diffusion coefficients of cation and anion in these ILs are studied using pulsed gradient spin-echo NMR technique. There are very few reports where electrochemically derived diffusion coefficients and self diffusion coefficients are available for comparison, so a new key concept in electrochemistry could be developed in this paper.     

INNOVATIVE APPLICATIONS OF IONIC LIQUIDS AS “GREEN” ENGINEERING LIQUIDS

Over the past decade, ionic liquids (ILs) have become one of the fastest growing “green” media for chemists and engineers due to their superb physicochemical properties. The applications of these remarkable salts in reactions and extraction processes have been extensively investigated and reviewed. This review, however, highlights recent advances of ILs as versatile “green” engineering liquids in a variety of industrial applications including heat transfer fluids, azeotrope-breaking liquids, lubricants, electrolytes, liquid crystals, supported IL membranes, plasticizers, and more. This review is not intended to be comprehensive, but rather to discuss the potentials of ILs for diverse industrial applications.     

Thermodynamic Modeling of Imidazolium-Based Ionic Liquids with the [PF6]− Anion for Separation Purposes

There is an increased interest in developing accurate tools to relate the physicochemical properties of ionic liquids (ILs) to their microscopic structure as this information is needed to speed up the design of new ionic liquids for chemical and industrial processes. Molecular models can be used for this purpose. We explore here the extended capabilities of a model previously developed in the context of soft-SAFT, by Andreu and Vega in 2007 to reproduce the thermodynamic behavior of imidazolium hexafluorophosphate-based ([C_nmim][PF₆]) ionic liquids. The molecular parameters optimized in the previous work have been used here in a transferable manner; some new members of the [C_nmim][PF₆] family have also been added, as new recent experimental data has been published. The interfacial tensions have been calculated using a Density Gradient Approach and the results have been compared with available experimental data. The solubility of carbon monoxide and hydrogen in those ILs has been studied in the range of temperatures and pressures of application for separation processes. Binary mixtures with other imidazolium ionic liquids with different anions have been calculated, in a predictive manner. Finally, calculations of mixtures of ionic liquids with water also show very good agreement with experimental data. This work highlights the importance of using a simple but robust thermodynamic model, including the right level of interactions, to accurately describe the properties of these highly non-ideal systems.     

离子液体的合成方法及其性能

离子液体具有较低的熔点、良好的导电性和可以忽略的蒸汽压等优点,引起了科学界和工业界的广泛瞩目。近年来,随着研究的日益深入,室温离子液体已经被开发和应用到诸多领域。本文对室温离子液体的合成、结构、性能等方面的研究现状进行了综述。     

High pressure solubility of CO2 in non-fluorinated phosphonium-based ionic liquids

High pressure solubility of carbon dioxide in three phosphonium-based ionic liquids has been measured experimentally. A synthetic method was used to measure vapor–liquid, vapor–liquid–liquid and liquid–liquid equilibria of carbon dioxide in the ionic liquids trihexyltetradecylphosphonium bromide [thtdp][Br], trihexyltetradecylphosphonium dicyanamide [thtdp][dca] and trihexyltetradecylphosphonium bis(2,4,4-trime-thylpentyl)phosphinate [thtdp][phos] for a temperature range of 271–363 K and up to 90 MPa. Furthermore, the densities and viscosities of these ILs have been measured in a temperature range of 293–363 K. The solubility of carbon dioxide in these ILs is (on mole fraction basis) significantly larger than most of the commonly used fluorinated imidazolium ionic liquids. The latter statement, however, does not hold for the [Br] and [dca] based IL if the solubility is compared on molality (mole/mass solvent) basis, where the solubility differences among physical ILs tends to vanish indicating a strong molecular weight effect. The solubility of carbon dioxide in [thtdp][phos], both on mole fraction and molality basis, is among the highest compared to all the other physical ILs reported so far in the literature. The Peng–Robinson equation of state in combination with Wong–Sandler mixing rules incorporating the NRTL Gibbs excess energy model was applied to represent the experimental data with acceptable accuracy.     

INNOVATIVE APPLICATIONS OF IONIC LIQUIDS AS “GREEN” ENGINEERING LIQUIDS

Over the past decade, ionic liquids (ILs) have become one of the fastest growing “green” media for chemists and engineers due to their superb physicochemical properties. The applications of these remarkable salts in reactions and extraction processes have been extensively investigated and reviewed. This review, however, highlights recent advances of ILs as versatile “green” engineering liquids in a variety of industrial applications including heat transfer fluids, azeotrope-breaking liquids, lubricants, electrolytes, liquid crystals, supported IL membranes, plasticizers, and more. This review is not intended to be comprehensive, but rather to discuss the potentials of ILs for diverse industrial applications.     

DENSITY ESTIMATION OF AMMONIUM-BASED IONIC LIQUIDS

Density is an important property of ionic liquids (ILs) that is required for process and product design. A recent article by Gardas and Coutinho (2008) reports the extended density correlation of ILs in wide ranges of temperature and pressure. However, they validated the density correlation only for ILs based on the following cations: imidazolium, pyridinium, pyrrolidinium, and phosphonium. The objective of this study is to validate the density correlation for ammonium-based ILs. The density model was tested against experimental densities available in the literature of ammonium-based ILs at a wide range of temperatures (273.15–393.15 K) and at 1 atm (0.1 MPa) of pressure. The results show that the predicted densities are in good agreement with available experimental literature values. The average absolute relative deviation (AARD) is 1.57%.     

Ionic Liquids as Extraction Solvents: Where do We Stand?

Abstract

The unique physicochemical properties of ionic liquids (ILs) and the relative ease with which these properties can be fine‐tuned by altering the cationic or anionic moieties comprising the IL have led to intense interest in their use as alternatives to conventional organic solvents in a wide range of synthetic, catalytic, and electrochemical applications. Recent work by a number of investigators has been directed at the application of ionic liquids in various separation processes, among them the liquid‐liquid extraction of metal ions. Although certain IL‐extractant combinations have been shown to yield metal ion extraction efficiencies far greater than those obtained with molecular organic solvents, other work suggests that the utility of ILs may be limited by solubilization losses and difficulty in recovering extracted metal ions. In this report, recent efforts to overcome these limitations are described, and progress both in achieving an improved understanding of the fundamental aspects of metal ion transfer into ILs and in devising viable IL‐based systems for metal ion separation is detailed. In addition, areas upon which future research efforts might profitably be focused are identified.     

离子液体在过渡金属催化炔及烯炔环合反应中的应用进展

概述了离子液体在过渡金属催化炔及烯炔类化合物环合反应中应用研究进展。由于固定了催化剂的离子液体能重复利用,既降低了反应成本,又对环境友好,因而具有广阔的应用前景。     

离子液体在生物催化中的应用

近年来,离子液体(ILs)以其独特的优势成为生物催化反应研究的热点,尤其是作为生物催化反应的溶剂或共溶剂的研究更是备受关注.许多酶能在ILs或其形成的两相体系或单相体系中保持催化活性.如目前研究最多的脂肪酶,有多种能在ILs中表现出活性稳定、反应选择性提高、产率提高等优良特性;某些蛋白酶在ILs中稳定性提高,具有酯酶的活性;β-半乳糖苷酶在ILs中的催化产率提高;全细胞在ILs中的催化反应效果也较好;但是也有某些酶,如纤维素酶、某些过氧化物酶等在ILs中活性会降低或丧失.因此有关这一方面的研究还有待进一步深入.     

功能化离子液体在二氧化碳吸收分离中的应用

吸收及分离二氧化碳是降低碳排放和应对全球气候变化的主要策略之一,这就必然要求全球科技工作者注重开发具有选择性高效吸收分离二氧化碳的新材料和新路线。作为近20多年来发展的一类代表性的新材料,离子液体（尤其是功能化离子液体）具有独特的物理化学性质,例如几乎没有蒸气压、液态温度范围大、热稳定性和化学稳定性好、电化学窗口宽、不可燃、结构-性质可调控等。这些性质使离子液体在二氧化碳吸收及分离领域受到广泛关注。重点综述了近5年（2015~2019）来功能化离子液体吸收分离二氧化碳的研究进展, 主要内容包括单位点离子液体、多位点离子液体、基于功能化离子液体的混合物、功能化离子液体杂化材料对二氧化碳的吸收分离。同时, 对目前该领域的发展所面临的主要问题和进一步的研究工作进行了分析讨论。     

Synthesis of Bipyridine‐Stabilized Rhodium Nanoparticles in Non‐Aqueous Ionic Liquids: A New Efficient Approach for Arene Hydrogenation with Nanocatalysts

A new approach to stabilize metal nanoparticles with polynitrogen ligands in ionic liquids (ILs) is described. Zerovalent metal nanospecies in the size range of 2.0 nm were easily prepared in various ionic liquids by chemical reduction of a rhodium salt with an excess amount of sodium borohydride (NaBH₄) and efficiently stabilized by 2,2′‐bipyridine. The influence of the bipyridine ratio in various ILs according to the nature of the cation‐anion association was investigated. These nanocatalysts were evaluated in the hydrogenation of aromatic compounds in ILs under various catalytic conditions (P=1–40 bar, T=20–80 °C).