Gas solubility in long‐chain imidazolium‐based ionic liquids

The gas solubility in 1‐dodecyl‐3‐methylimidazolium [C₁₂MIM] based ionic liquids (ILs) was measured at temperatures (333.2, 353.2, and 373.2) K and pressures up to 60 bar for the first time. The popular UNIFAC‐Lei model was successfully extended to long‐chain imidazolium‐based IL and gas (CO₂, CO, and H₂) systems. The free volume theory was used to explain the gas solubility and selectivity in imidazolium‐based ILs by calculating the fractional free volume and free volume by the COSMO‐RS model. Furthermore, the excess enthalpy of gas‐IL system was concerned to provide new insights into temperature dependency of gas (CO₂, CO, and H₂) solubility in ILs. The experimental data, calculation, and theoretical analysis presented in this work are important in gas separations with ILs or supported ionic liquid membranes. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1792–1798, 2017     

Correlating structure with ionic conductivity in bis(phosphonium)‐containing [NTf2] thiol–ene networks

Thiol–ene photopolymerization was employed in order to prepare a series of covalently crosslinked bis(phosphonium)‐containing poly(ionic liquid) (PIL) networks. While the counteranion was held constant (NTf₂), the structure of the bis(phosphonium)‐containing ‘ene’ monomer was varied in order to explore the breadth of thermal, mechanical and conductive properties available for this system. Towards this end, it was determined that more flexible spacers within the cationic monomer led to PIL networks with lower T_g values and higher conductivities. Most notable was a two‐ to three‐orders‐of‐magnitude increase in ionic conductivity (from 10^?9 to 10^?6 S cm^?1 at 30 °C, 30% relative humidity) when the R group on phosphonium was changed from phenyl to isopropyl. Changing the functional group ratio to off‐stoichiometry also led to a slight increase in conductivity. Although the thermal stability (T_d5%) of the phosphonium ionic liquid monomers was found to be significantly higher (>400 °C) than that of analogous imidazolium monomers, this improvement was not observed to directly transfer over to the polymer where a two‐step decomposition pathway was observed. The first step is attributed to the thiol monomer backbone while the second step correlates well with decomposition of the phosphonium portion of the PIL. © 2019 Society of Chemical Industry     

Application of optical microscopy as a screening technique for cellulose and lignin solvent systems

Rapid and facile screening techniques to determine the effectiveness of solvents for cellulose or biomass dissolution can advance biomass processing research. Here, we report the use of a simple optical microscopy method to screen potential cellulose and lignin solvents. The described methodology was used to screen the dissolution of cellulose and lignin in two imidazolium‐based ionic liquids (ILs), two phosphonium‐based ILs, as well as a N,N‐dimethylacetamide/lithium chloride (DMAc/LiCl) solution in less time than other techniques. The imidazolium‐based ILs and the DMAc/LiCl were found to dissolve both cellulose and lignin. Also, it was observed that one of the phosphonium‐based ILs dissolved lignin and not cellulose, demonstrating a potential for biomass fractionation applications. © 2011 Canadian Society for Chemical Engineering     

Ionic Liquid with Silyl Substituted Cation: Thermophysical and CO2/N2 Permeation Properties

Novel functionalized ionic liquid (IL) combining an imidazolium‐based cation with branched alkyl chain bearing silyl group, 1‐methyl‐3‐(2‐methyl‐3‐(trimethylsilyl)propyl)imidazolium ([Si?C₁?C₃‐mim]⁺), and bis(trifluoromethylsulfonyl)imide ([NTf₂]^?) anion was synthesized and its thermophysical properties (density, viscosity, surface tension, surface entropy and enthalpy, thermal stability) were studied in a wide temperature range and compared with those of ILs having linear alkyl ([C_n‐mim][NTf₂]) and siloxane ([(SiOSi)C₁mim][NTf₂]) side chains. It was found that at 25 °C [Si?C₁?C₃‐mim][NTf₂] is a liquid with dynamic viscosity of 224 cP (224 mPa s) and density of 1.32 g cm^?3. The presence of side branched alkyl chain with trimethylsilyl end‐group prevents crystallization of IL and leads to higher viscosities and lower densities in comparison with commonly known [C_n‐mim][NTf₂] (n=2–4). As surface excess enthalpy was found to be in the lower end of the usual range of values for ILs, the interactions between silyl‐functionalized cation and [NTf₂] anion can be considered as relatively weak. Finally, [Si?C₁?C₃‐mim][NTf₂] was used for the preparation of polymer supported ionic liquid membranes (SILMs) and their CO₂ and N₂ permeation properties at 20 °C and 100 kPa were determined: permeability PCO₂=311, PN₂=12 Barrer, diffusivity DCO₂=115×10¹², DN₂=227×10¹² m² s^?1 and CO₂/N₂ permselectivity αCO₂/N₂=25.3.     

An investigation into the degree and rate of polymerization of poly(methyl methacrylate) in the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate

Room‐temperature ionic liquids (ILs), including 1‐butyl‐3‐methylimidazolium hexafluorophosphate, [bmim⁺][PF₆^?], were investigated as replacements for volatile organic compounds in the free‐radical solution polymerization of poly(methyl methacrylate) (PMMA). The latter was synthesized in benzene and [bmim⁺][PF₆^?] at 70 °C via a free‐radical process and the degree and rate of polymerization were compared based on the solvent used. The degree of polymerization was found to be five times higher in [bmim⁺][PF₆^?] than in benzene, while the rate of reaction was approximately four times faster in [bmim⁺][PF₆^?]. The results indicate the potential for using ILs to produce high‐molecular‐weight polymers and block structures based on the increased free‐radical stability in ILs. Copyright © 2004 Society of Chemical Industry     

Antitumor Activity of Ionic Liquids Based on Ampicillin

Significant antiproliferative effects against various tumor cell lines were observed with novel ampicillin salts as ionic liquids. The combination of anionic ampicillin with appropriate ammonium, imidazolium, phosphonium, and pyridinium cations yielded active pharmaceutical ingredient ionic liquids (API‐ILs) that show potent antiproliferative activities against five different human cancer cell lines: T47D (breast), PC3 (prostate), HepG2 (liver), MG63 (osteosarcoma), and RKO (colon). Some API‐ILs showed IC₅₀ values between 5 and 42 nM , activities that stand in dramatic contrast to the negligible cytotoxic activity level shown by the ampicillin sodium salt. Moreover, very low cytotoxicity against two primary cell lines—skin (SF) and gingival fibroblasts (GF)—indicates that the majority of these API‐ILs are nontoxic to normal human cell lines. The most promising combination of antitumor activity and low toxicity toward healthy cells was observed for the 1‐hydroxyethyl‐3‐methylimidazolium–ampicillin pair ([C₂OHMIM][Amp]), making this the most suitable lead API‐IL for future studies.     

Expanding the chemistry of single‐ion conducting poly(ionic liquid)s with polyhedral boron anions

The synthesis of a new family of single‐ion conducting random copolymers bearing polyhedral boron anions is reported. For this purpose two novel ionic monomers, namely [B₁₂H₁₁(OCH₂CH₂)₂OC(?O)C(CH₃)?CH₂]^2?[(C₄H₉)₄N⁺]₂ and [8‐(OCH₂CH₂)₂OC(?O)C(CH₃)?CH₂‐3,3′‐Co(1,2‐C₂B₉H₁₀)(1′,2′‐C₂B₉H₁₁)]^?K⁺, having methacrylate function, diethylene glycol bridge and closo‐dodecaborate or cobalt bis(1,2‐dicarbollide) anions were designed. Such monomers differ from previously reported ones by (i) chemically attached highly delocalized boron anions, by (ii) valency of the anion (divalent anion and monovalent one) and by (iii) the presence of oxyethylene flexible spacer between the methacrylate group and bonded anion. Their free radical copolymerization with poly(ethylene glycol) methyl ether methacrylate and subsequent ion exchange provided lithium‐ion conducting polyelectrolytes showing low glass transition temperature (?53 to ?49 °C), ionic conductivity up to 9.1 × 10^?7 S cm^?1, lithium transference number up to 0.61 (70 °C) and electrochemical stability up to 4.1 V versus Li⁺/Li (70 °C). The incorporation of propylene carbonate (20–40 wt%) into the copolymers resulted in the enhancement of their ionic conductivity by one order of magnitude and significantly increased their electrochemical stability up to 4.7 V versus Li⁺/Li (70 °C). © 2019 Society of Chemical Industry     

Optimization of Enzymatic Synthesis of Tricaprylin in Ionic Liquids by Response Surface Methodology

Ten 1,3‐dialkylimidazolium‐based ionic liquids (ILs) have been investigated as media for the enzymatic synthesis of tricaprylin, in comparison with the conventional organic solvent hexane. The results suggested that the esterification activity of Novozym 435 was higher than Lypozyme RM IM in all the ILs assayed. Novozym 435 showed higher catalytic activity in ILs with anions Tf₂N^? and PF₆^? than in BF₄^? and hexane. FTIR analysis of the secondary structure of the lipase indicated that a smaller decrease of the α‐helix was observed in [C₄MIM] Tf₂N and [C₄MIM] PF₆ than [C₄MIM] BF₄ and hexane, indicating that the anions of ILs might be a key factor for the activity of lipase in ILs. Process parameters (amount of lipase, caprylic acid/glycerol molar ratio, temperature and their interactive effects) were optimized in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄MIM]PF₆) using Novozym 435 by response surface methodology. When the reactions were performed with the lipase amount of 6.1 % substrate mass at a caprylic acid/glycerol molar ratio of 4.5:1 and 66.7 °C, a higher yield was reached up to 92.4 %.     

Photoinitiated polymerization in ionic liquids and its application

Ionic liquids (ILs) are low‐melting organic salts often liquid at room temperature, whose unique properties are the reason of increasing interest for their applications as solvents, reaction media and functional additives. The exceptional properties of ILs have proved to be particularly useful in polymer science giving the potential to produce polymeric materials with improved properties or to immobilize ILs in polymer matrices while keeping their special characteristics. One of the possibilities is polymerization in ILs which can also affect positively polymerization reactions. An especially attractive technique is photopolymerization due to the ease of process control, short reaction time and ambient working temperature. This review gives a literature survey of developments in photopolymerization processes carried out in ILs as well as applications of these processes. It covers both the photopolymerization in ILs as well as photopolymerization of IL monomers. The first part presents a short overview of physicochemical and photochemical properties of ILs; it includes also photochemical reactions and photoinitiation of polymerization in ILs. The second part covers both the basic research (kinetics of photopolymerization including polymerization rate coefficients and polymerization of IL monomers) as well as applications of UV‐induced polymerization in ILs. © 2016 Society of Chemical Industry     

UNIFAC model for ionic liquid‐CO (H2) systems: An experimental and modeling study on gas solubility

The universal quasichemical functional‐group activity coefficients (UNIFAC) model for ionic liquids (ILs) has become notably popular because of its simplicity and availability via modern process simulation softwares. In this work, new group binary interaction parameters (α_mn and α_nm) between CO (H₂) and IL groups were obtained by correlating the solubility data in pure ILs at high temperatures (above 273.2 K) collected from the literature. the solubility of CO in [BMIM]⁺[BF₄]^?, [OMIM]⁺[BF₄]^?, [OMIM]⁺[Tf₂N]^?, and their mixtures, as well as that of H₂ in [EMIM]⁺[BF₄]^?, [BMIM]⁺[BF₄]^?, [OMIM]⁺[Tf₂N]^?, and their mixtures, at temperatures from 243.2 to 333.2 K and pressures up to 6.0 MPa were measured. The UNIFAC model was observed to well predict the solubility in pure and mixed ILs at both high (above 273.2 K) and low (below 273.2 K) temperatures. Moreover, the selectivity of CO (or H₂) to CO₂ in ILs increases with decreasing temperature, indicating that low temperatures favor for gas separation. © 2014 American Institute of Chemical Engineers AIChE J 60: 4222–4231, 2014     

Photoinitiated polymerization in ionic liquids: Kinetics and viscosity effects

The photo-induced polymerization of poly(ethylene glycol) dimethacrylate and poly(ethylene glycol) monomethacrylate (crosslinking and linear, resp.) in four imidazolium-based ionic liquids (ILs) containing the same cation or the same anion in pairs is reported. The kinetic studies were accompanied by detailed viscosity measurements, which showed the occurrence of an interesting phenomenon - a viscosity synergism in monomer/IL mixtures (i.e. the viscosity of the mixture is higher than the simple additive combination of viscosities of the two components). Viscosity synergism, very important for kinetic considerations, is especially strong for ILs of low viscosity and its magnitude depends on the monomer structure. The polymerization conducted in ILs was considerably faster than in a reference solvent. The propagation rate coefficients were influenced mainly by the anion structure whereas the termination rate coefficients by viscosity of the initial monomer/IL mixture (taking into account the synergistic effect). FTIR studies showed the existence of specific interactions between the carbonyl group in the monomer and C₂-H of the imidazolium ring; the polymerization rates were directly related to the magnitude of the monomer/IL interaction.     

Improved Stability and Catalytic Activity of Palladium Nanoparticle Catalysts using Phosphine‐Functionalized Imidazolium Ionic Liquids

Palladium nanoparticles (Pd NPs) stabilized by 6 different phosphine‐functionalized ionic liquids (PFILs) were synthesized in imidazolium‐based ionic liquids (ILs) using H_2(g) (4 bar) as a reductant. Characterization showed well‐dispersed particles of ∼3 nm (TEM) and confirmed the PFIL stabilization of the NPs (XPS). The PFILs were composed of an imidazolium functionality separated from the phosphine group by a propyl or undecyl chain. The counter anions for both FILs and IL solvents were chosen from N‐bis(trifluoromethanesulfonyl)imide (Tf₂N⁻), trifluoromethanesulfonate (TfO⁻) or hexafluorophosphate (PF₆⁻). Colloidal suspensions of the Pd NPs were employed as biphasic hydrogenation catalysts for the reduction of the olefinic bond in styrene under mild conditions (50 °C, 4 bar H_2(g), 1.5 h). The PFIL‐stabilized Pd NPs were effective hydrogenation catalysts and showed superior activity and recyclability over NPs synthesized in the absence of PFILs. Poisoning tests of the Pd NP catalysts and characterization of the electronic properties of the phosphine were also performed.     

Synthesis of poly(ethylene terephthalate) in benzyl imidazolium ionic liquids

In order to improve the method of synthesis of poly(ethylene terephthalate) (PET), a series of ionic liquids (ILs) based on benzyl imidazolium ([YBMIM][X], Y = NO₂, CH₃, F; B = benzyl; X = Tf₂N) were used to investigate the formation of PET at low temperature and pressure. High molecular weight PET (M_w up to 2.6 × 10⁴ g mol^?1) was obtained by two‐step polycondensation in these ILs at lower temperature (230–240 °C) than with traditional melt polycondensation (270–290 °C). Moreover, the molecular weight of the resulting PET was found to depend on the activities of the catalysts used in the ILs. The catalysts (Sb₂(OCH₂CH₂O)₃, Sb(OAc)₃, Sb₂O₃) used in the preparation of PET have little effect on the thermostability of the ILs. The ILs can decrease the viscosity of the reaction system, and thus small molecules can be easily removed. Copyright © 2012 Society of Chemical Industry     

Polymerizable ionic liquids for the preparation of polystyrene/clay composites

Polymerizable ionic liquids (ILs) 1‐methyl‐3‐(4‐vinylbenzyl)imidazolium chloride, 1‐hexyl‐3‐(4‐vinylbenzyl)imidazolium chloride and 1‐dodecyl‐3‐(4‐vinylbenzyl)imidazolium chloride were prepared and used as new surfactants for the modification of montmorillonite (MMT). Functionalized MMTs were prepared by cationic exchange between sodium MMT and each of the ILs. Polystyrene (PS)/MMT composites were subsequently prepared by in situ intercalative free radical polymerization of styrene containing dispersed organophilic MMT. Exfoliation of MMT in the PS matrix was achieved only for MMT functionalized with the 1‐dodecyl‐3‐(4‐vinylbenzyl)imidazolium‐based IL as revealed by X‐ray diffraction and electron microscopy. The exfoliated composites showed good transparency and higher decomposition temperature than virgin polymer matrix, particularly pronounced under air atmosphere (ΔT_max = 66 °C), data comparable to or even greater than those reported in the literature for exfoliated PS nanocomposites. Copyright © 2012 Society of Chemical Industry     

Antibacterial Activities of Five Cationic Gemini Surfactants with Ethylene Glycol Bisacetyl Spacers

A series of cationic gemini surfactants containing two dimethylalkylammonium chains linked by ethylene glycol bisacetyl spacers were synthesized [G_m‐AnA‐m, G = gemini surfactant, m = 12 (–C₁₂H₂₅), 14 (–C₁₄H₂₉), or 16 (–C₁₆H₃₃), A = acetyl, and n = 2, 3, or 4 is the number of ethylene glycol units in the spacers]. Because of the inductive effect of the oxygen atom in the spacer, acylation can take place using chloroacetyl chloride instead of bromoacetyl bromide which helps to limit the use of environmentally harmful reagents. Critical micelle concentrations were determined using conductivity measurements. The antibacterial activities of the surfactants against Gram‐positive bacterium Staphylococcus aureus and Gram‐negative bacterium Escherichia coli were evaluated from the minimum inhibitory concentration (MIC), minimum bacterial concentration, a time–kill study, and the inhibitory zone. Increasing the length of the spacer did not result in an obvious change of antibacterial activity. However, increasing the length of the alkyl chain apparently increased the antibacterial activity against S. aureus but decreased the antibacterial activity against E. coli. The G_{12‐A2A‐12} surfactant had the lowest CMC of 1.26 mmol L^?1 and exhibited the best antibacterial activity with a MIC of 32 μg mL^?1 toward S. aureus and 64 μg mL^?1 toward E. coli in the presence of 10⁵ CFU of bacteria. This work indicated that these cationic gemini surfactants have potential applications as antibacterial agents and emulsifiers.     

Screening ionic liquids as candidates for separation of acid gases: Solubility of hydrogen sulfide,methane, and ethane

The solubility of the major constituents of natural gas in ionic liquids (ILs) can be used to identify their potential for acid gas removal from a producing gas stream. We have developed models for the solubility of H₂S, CH₄, and C₂H₆ in ILs at typical conditions encountered in natural gas treatment. In this work, a conductor‐like screening model for realistic solvation was used to predict the activity coefficients for solutes in ILs and a cubic EOS was used for vapor‐phase corrections from ideality. Empirical correlations were developed to extrapolate solubilities where experimental data are not available at desired conditions; targeted in this study at 298.15 K and 2000 kPa. Over 400 possible ILs were ranked based on the higher selectivity of absorption of CO₂ and H₂S over CH₄ and C₂H₆. The best 15% (58) of promising ILs for sour gas treatment predominantly contain the anions BF₄, NO₃, and CH₃SO₄ and the cations N₄₁₁₁, pmg, and tmg. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2993–3005, 2013     

Design and screening of ionic liquids for C2H2/C2H4 separation by COSMO‐RS and experiments

Ionic liquids (ILs) have been proposed as promising solvents for separating C₂H₂ and C₂H₄, but screening an industrially attractive IL with high capacity from numerous available ILs remains challenging. In this work, a rapid screening method based on COSMO‐RS was developed. We also present an efficient strategy to improve the C₂H₂ capacity in ILs together with adequate C₂H₂/C₂H₄ selectivity with the aid of COSMO‐RS. The essence of this strategy is to increase molecular free volume of ILs and simultaneously enhance hydrogen‐bond basicity of anions by introducing flexible and highly asymmetric structures, which is validated by a new class of tetraalkylphosphonium ILs featuring long‐chain carboxylate anions. At 298.1 K and 1 bar, the solubility of C₂H₂ in ILs reaches 0.476 mol/mol IL, very high for a physical absorption, with a selectivity of up to 21.4. The separation performance of tetraalkylphosphonium ILs to the mixture of C₂H₂/C₂H₄ was also evaluated. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2016–2027, 2015     

How imidazolium-based ionic liquids solubilize the poorly soluble ibuprofen? A theoretical study

Molecular dynamics simulations were performed to study combinations of [AcO]⁻, [TfO]⁻, [BF₄]⁻, and [PF₆]⁻ anions paired with imidazolium cations of increasing alkyl chain length to elucidate the roles of anions and cations in solvating ibuprofen. Our simulation results revealed that ionic liquids (ILs) with strong ibuprofen solvation capacity should possess strong van der Waals force from cations and strong hydrogen bond (HB) from anions. Accordingly, it was found that ILs containing anions with strong HB acceptability, such as [AcO]⁻ anion, were the best effective solvent for ibuprofen solvation, while the longer alkyl chain in the imidazolium cations decrease the polarity, thus increasing the affinity with ibuprofen. Therefore, it was suggested that the heterocyclic structure of imidazolium cation with moderate polarity and longer alkyl chain is a promising cation candidate, whereas the anions which have a strong HB acceptability and substituents without electron withdrawing groups are beneficial. The obtained results can provide useful information for rational design and selection of new ILs to dissolve insoluble drugs.     

Can Kosmotropic Salt/Chaotropic Ionic Liquid (Salt/Salt Aqueous Biphasic Systems) be Used to Remove Pertechnetate From Complex Salt Waste?

Abstract

Aqueous solutions of water‐structuring, kosmotropic salts (e.g., salts of PO₄ ^3?, HPO₄ ^2?, CO₃ ^2?) will salt‐out water‐destructuring chaotropic ionic liquids (ILs) (e.g., 1‐butyl‐3‐methylimidazolium chloride, ([C₄mim]Cl)) forming salt/salt aqueous biphasic systems (ABS). The chaotropic pertechnetate (TcO₄ ^?) anion will partition without the use of an extractant into the IL‐rich phase. These complex salt/salt ABS are not unlike the complex and salt‐rich Hanford tank waste, and thus have been used here as a simple model to show effectiveness in the partitioning of TcO₄ ^? from such tank waste into an IL‐rich phase.     

Preparation of epoxy/MCDEA networks modified with ionic liquids

Ionic liquids based on imidazolium, pyridinium and phosphonium with long alkyl chain were used to develop epoxy networked materials cured at high temperature, with 4,4′-methylene-bis 3-chloro-2,6-diethylaniline (MCDEA). Imidazolium- and pyridinium-based ILs decreased the onset curing temperature suggesting an accelerating effect, whereas those based on phosphonium salts exerted only a marginal effect on the curing process. The presence of the ILs resulted in a decrease of the glass transition temperature and this effect was less pronounced in systems containing phosphonium-based IL with [PF₆] as the counteranion. The storage modulus below the Tg increased with the addition of ionic liquid suggesting an improvement of stiffness due to the interactions between the ILs and the epoxy matrix. Such interactions were also confirmed by rheological properties. Considering different ionic liquids, those constituted by phosphonium salts were effectively confined inside the epoxy networks and that containing iodide as the counteranion presented the best thermal stability, being indicated for assessing epoxy-based systems with high curing temperature.