Application of ionic liquids as low-volatility plasticizers for PMMA

Room temperature ionic liquids (ILs) based on imidazolium salts, were found to be excellent plasticizers for poly(methyl methacrylate), with improved thermal stability, and the ability to reduce glass transition temperatures to near 0 °C. Because ILs have environmentally benign properties, they can be used in place of traditional chemicals in numerous products and processes. In this work, PMMA was formulated using dioctyl phthalate, DOP, as a traditional plasticizer, and properties were compared to PMMA plasticized with two ILs: butyl methylimidazolium/hexafluorophosphate, [bmim⁺][PF₆⁻], and hexyl methylimidazolium/hexafluorophosphate, [hmim⁺][PF₆⁻]. Formulations incorporated up to 30 vol.% DOP and 50 vol.% ILs. Bulk and plasticized polymers were characterized for glass transition temperature, elastic modulus, and the thermal stability of the plasticizers.     

Synthesis of methyl orange using ionic liquids

Two ionic liquids were synthesized, each system consisting of the 1-hexyl-3-methylimidazolium ion ([hmim]⁺) as the cation and either hexafluorophosphate ([PF₆]⁻), or perchlorate ([ClO₄]⁻) as the anions. This study involves the synthesis of methyl orange (4-[[(4-dimethylamino)phenyl]-azo] benzene sulfonic acid sodium salt) using the ionic liquids as replacement solvents for the reaction. The advantage of using ionic liquids as substitutes for organic solvents includes: recyclable/reclaimable solvents, stabilization of intermediates and higher product yields. The 1-hexyl-3-methylimidazolium derivatives can be used for syntheses conducted at low temperatures and are less toxic than typical organic solvents.     

Volumetric and compressibility behaviour of ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate and tetrabutylammonium hexafluorophosphate in organic solvents at T = 298.15 K

Density and speed of sound measurements have been made on the systems containing the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and some organic solvents having a wide range of dielectric constants. Similar studies have been carried out for tetrabutylammonium hexafluorophosphate ([TBA][PF₆]), which has common anion ([PF₆]⁻) with the studied ionic liquid. For the systems investigated, the apparent molar volumes and apparent molar isentropic compressibilities were determined and fitted to the Redlich–Mayer and the Pitzer equations from which the corresponding limiting values were obtained. These limiting values were used to obtain some information about ion–solvent interactions. Furthermore, using the ionic limiting apparent volume values for [TBA]⁺ from the literature and limiting apparent molar volume for the ionic liquid and [TBA][PF₆] obtained in this work, the ionic limiting apparent molar volume values for the cation [BMIM]⁺ in different organic solvents were also estimated.     

Hydrogen substitution effect on the solubility of perhalogenated compounds in ionic liquid [bmim][PF6]

Solubility behaviors of binary mixtures of CFCl₃ (R-11), CFCl₂-CF₂Cl (R-113), CHCl₃ (R-20), CDCl₃ (R-20-d), CHCl₂–CF₃ (R-123) with room-temperature ionic liquid [bmim][PF₆] (1-butyl-3-methylimidazolium hexafluorophosphate) have been investigated using the volumetric and cloud-point methods, since all the systems show liquid–liquid equilibria (LLE). Large immiscibility (LLE) gaps of the perhalogenated compounds (R-11 and R-113) in the ionic liquid have been drastically reduced by the addition of only one hydrogen (or deuterium) in these compounds. The R-123 + [bmim][PF₆] binary system belongs to the Type-V fluid behavior. Noticeably large negative values (−2 to −8 cm³ mol⁻¹) of the excess molar volume in the ionic liquid-rich side solution have been observed for all the present systems. Experimental LLE data have been well correlated by the use of the NRTL (non-random two liquid) activity coefficient model.     

Use of 1-alkyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquids as chelate extraction solvent with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione

Possible use of room temperature ionic liquids (RTILs) as chelate extraction solvent was evaluated by using 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF₆]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF₆]). These RTILs showed high extraction performance for divalent metal cations with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta). The extracted metals were back-extracted into 1 mol dm⁻³ nitric acid quantitatively. Furthermore, the extracted species were estimated as neutral hydrated complexes M(tta)₂(H₂O)_n (n= 1 or 2) for M = Ni, Cu and Pb and anionic complexes M(tta)₃⁻ for M = Mn, Co, Zn and Cd.     

The preparation of sol-gel materials doped with ionic liquids and trialkyl phosphine oxides for yttrium(III) uptake

A new material (IL923SGs) composed of ionic liquids and trialkyl phosphine oxides (Cyanex 923) for Y(III) uptake was prepared via a sol-gel method. The hydrophobic ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate (C₈mim⁺PF₆⁻) was used as solvent medium and pore templating material. The extraction of Y(III) by IL923SGs was mainly due to the complexation of metal ions with Cyanex 923 doped in the solid silica. Ionic liquid was stably doped into the silica gel matrix providing a diffusion medium for Cyanex 923, and this will result in higher removal efficiencies and excellent stability for metal ions separation. IL923SGs were also easily regenerated and reused in the subsequent removal of Y(III) in four cycles.     

Ternary (liquid + liquid) equilibria of the azeotrope (ethyl acetate + 2-propanol) with different ionic liquids at T = 298.15 K

Experimental (liquid + liquid) equilibria involving ionic liquids {1,3-dimethylimidazolium methyl sulfate (MMIM MeSO₄)}, {2-propanol + ethyl acetate + 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF₆)} and {2-propanol + ethyl acetate + 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIM PF₆)} were carried out to separate the azeotropic mixture ethyl acetate and 2-propanol. Selectivity and distribution ratio values, derived from the tie-lines data, were presented in order to analyze the best separation solvent in a liquid extraction process. Experimental (liquid + liquid) equilibria data were compared with the correlated values obtained by means of the NRTL, Othmer-Tobias and Hand equations. These equations were verified to accurately correlate the experimental data.     

Extraction of Metal Ions from Aqueous Solutions Using Imidazolium Based Ionic Liquids

This article represents a step towards how to choose an ionic liquid as the solvent to improve metal ion (Ag⁺ and Pb²⁺) extraction. The liquid-liquid solvent extraction is proposed with the following imidazolium ionic liquids (ILs): 1-ethyl-3-ethylimidazolium, or 1-butyl-3-ethylimidazolium, or 1-hexyl-3-ethylimidazolium bis{(trifluoromethyl)sylfonyl}imide [EEIM][NTf₂], or [BEIM][NTf₂], or [HEIM][NTf₂], or 1-butyl-3-ethylimidazolium hexafluorophosphate [BEIM][PF₆], or 1-hexyl-3-ethylimidazolium hexafluorophosphate [HEIM][PF₆] and the popular 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] for comparison. The effect of anion type (NTf₂⁻ versus PF₆⁻) and the effect of structural components of an ionic liquid including alkyl chain length at the cation and the ethyl substituent instead methyl at the cation, on the extraction and re-extraction processes by using dithizone as a metal chelator, were studied at 296 K. Dithizone was employed to form neutral metal-dithizone complexes with heavy metal ions to extract them from aqueous solution into the ILs. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users. Presented at the 236th ACS National Meeting, August 17–21, Philadelphia, USA.     

Solubilities of imidazolium-based ionic liquids in aqueous salt solutions at 298.15 K

The solubilities of ionic liquids in the ternary systems (ionic liquid + H₂O + inorganic salt) were reported at 298.15 K and atmospheric pressure. The examined ionic liquids are [C₄mim][PF₆] (1-n-butyl-3-methylimidazolium hexafluorophosphate), [C₈mim][PF₆] (1-n-octyl-3-methylimidazolium hexafluorophosphate), and [C₈mim][BF₄] (1-n-octyl-3-methylimidazolium tetrafluoroborate). The examined inorganic salts are the chloride-based salts (sodium chloride, lithium chloride, potassium chloride, and magnesium chloride) and the sodium-based salts (sodium thiocyanate, sodium nitrate, sodium trifluoroacetate, sodium bromide, sodium iodide, sodium perchlorate, sodium acetate, sodium hydroxide, sodium dihydrogen phosphate, sodium phosphate, sodium tetrafluoroborate, sodium sulfate, and sodium carbonate). The effects of the cations and the anions of the ionic liquids and of the inorganic salts on the solubility of the ionic liquids in the ternary solutions were systematically compared and discussed.     

Ultrasound-assisted ionic liquid dispersive liquid-phase micro-extraction: A novel approach for the sensitive determination of aromatic amines in water samples

Ultrasound-assisted ionic liquid dispersive liquid-phase micro-extraction was developed for the determination of four aromatic amines such as 2,4-dichloroaniline, 1-naphthylamine, 6-chloroanline and N,N-dimethylaniline. High-performance liquid chromatography coupled with UV detector was used for the determination of aromatic amines. In the novel procedure, 1-hexyl-3-methylimidazolium hexafluorophosphate [C₆MIM] [PF₆] was dispersed into the aqueous sample solution as fine droplets by ultrasonication, and which promoted the analytes more easily migrate into the ionic liquid phase. Variable affecting such as the volume of [C₆MIM] [PF₆], sample pH, ultrasonication time, extraction time, centrifuging time have been investigated in detail. The proposed method has been found to have excellent detection sensitivity with limits of detection (LOD, S/N = 3) in the range of 0.17–0.49 μg L⁻¹ and precisions in the range of 2.0–6.1% (RSDs, n = 6). This method has been also successfully applied to analyze the real water samples and good spiked recoveries over the range of 92.2–119.3% were obtained.     

Electropolymerization of ionic liquid substituted polyphenylene as supercapacitors materials

A new type of polyphenylene, ionic liquid (IL) 1,3-methylimidazolium hexafluorophosphate substituted, has been prepared by electrodeposition on Au electrode surface via pulse galvanostatic method in 1-butyl-3-methylimidazolium hexafluorophosphate solution. The obtained polymer film had a spherulitic morphology with smallest grains of around 500 nm. Infrared spectrometry revealed that polyphenylene was deposited to a certain extent. The capacitive behavior of the IL substituted polyphenylene was investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge method in 0.2 mol L⁻¹ H₂SO₄ aqueous solutions or pure IL [bmim]PF₆. The specific capacitance of the polymer at the charge–discharge current density of 1 mA cm⁻² equaled 206 F g⁻¹ in acidic aqueous solution or 164 F g⁻¹ in [bmim]PF₆. Additionally, excellent charge–discharge cycle stability (over 85% value of specific capacitance remained after 600 charge–discharge cycles) and power characteristics of the polymer electrode were observed in both electrolytes.     

A study on the liquid–liquid equilibria of 1-alkyl-3-methylimidazolium hexafluorophosphate with ethanol and alkanes

This work demonstrates the ability of the 1-alkyl-3-methylimidazolium hexafluorophosphate to act as an extraction solvent in petrochemical processes for the removal of alkanes from their azeotropic mixture with ethanol. LLE (liquid–liquid equilibrium) of the ternary systems hexane + ethanol + 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIM PF₆) or 1-octyl-3-methylimidazolium hexafluorophosphate (OMIM PF₆) and heptane + ethanol + OMIM PF₆ are carried out at 298.15 K and atmospheric pressure. Experimental liquid–liquid data are correlated by using different equations. The solute distribution ratio and the selectivity, determined from tie-line data, suggest the efficiency of the ILs used as solvents. A comparison with other IL, in terms of solvent capacity, is included. The liquid–liquid extraction process is simulated by using conventional software and the obtained results are shown.     

Study on the phase behaviour and thermodynamic properties of ionic liquids containing imidazolium cation with ethanol at several temperatures

Experimental densities, speeds of sound and refractive indices of the binary mixtures of ethanol with MMIM MeSO₄ (1,3-dimethylimidazolium methyl sulfate), BMIM MeSO₄ (1-butyl-3-methylimidazolium methyl sulfate), BMIM PF₆ (1-butyl-3-methylimidazolium hexafluorophosphate), HMIM PF₆ (1-hexyl-3-methylimidazolium hexafluorophosphate) and OMIM PF₆ (1-methyl-3-octylimidazolium hexafluorophosphate) were determined from T = (293.15 to 303.15) K. Excess molar volumes, changes of refractive index on mixing and deviations in isentropic compressibility for the above systems were calculated. The (liquid + liquid) equilibrium (LLE) data of (IL + ethanol) were carried out experimentally and the NRTL and UNIQUAC correlative equation was applied to these mixtures.     

Increased paraoxon detection by acetylcholinesterase inactivation with ionic liquid additives

This is the first study using ionic liquids (ILs) as additive in the aqueous solvent medium for detection of paraoxon by acetylcholinesterase inhibition method. A systematic comparison of various ILs with organic solvents has been made. The aqueous buffer solution containing ionic liquid ethylpyridinium hexafluorophosphate [EtPy]⁺[PF₆]⁻ has been found to give the best results. The inhibition kinetic follows the first order model. Ionic liquids modified aqueous solutions show the potential to provide a promising and effective medium in detection of paraoxon with acetylcholinesterase.     

Homogeneous ionic liquid microextraction of the active constituents from fruits of Schisandra chinensis and Schisandra sphenanthera

Homogeneous ionic liquid microextraction (HILME) was developed for the extraction of schizandrin, schisantherin A and deoxyschizandrin from Schisandra chinensis and Schisandra sphenanthera. 1-Butyl-3-methylimidazolium tetrafluoroborate ([C₄MIM][BF₄]) aqueous solution was used as extraction solvent, and ammonium hexafluorophosphate ([NH₄][PF₆]) was used as ion-pairing agent. 1-Butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]), which is barely soluble in water, was formed in situ, and was used as sample solution. High-performance liquid chromatography (HPLC) was employed for separation and determination of the analytes. The calibration curve showed good linear relationship (r > 0.9998). The recoveries were between 69.71% and 88.33% with RSDs lower than 4.86%. External standard method was adopted in the proposed method, and internal standard method was applied for the evaluation of the proposed method. The two methods were compared and the results indicated that the proposed method was acceptable and simple. The HILME is free of volatile organic solvents, and represents lower expenditures of sample, extraction time and solvent, compared with ultrasonic and Soxhlet extraction. There was no obvious difference in the extraction yields of active constitutions obtained by the three extraction methods.     

Extraction-separation of Eu(III) and Th(IV) ions from nitrate media into a room-temperature ionic liquid

Application of a room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim⁺][PF₆ ^?]), in the extraction of Eu(III) and Th(IV) ions from nitrate media using tri-n-octylphosphine oxide (TOPO) as extractant is investigated. The results are compared with those obtained in dichloromethane. It is shown that the europium ions are extracted via a solvation mechanism by formation of [Eu(TOPO) ₃ ³⁺ ](NO₃ ^?)₃ species in both [C₄mim⁺][PF₆ ^?] and dichloromethane. Nevertheless, application of the studied RTIL makes a significant improvement in the extraction efficiency of europium ions. A different attitude was observed for the extraction of thorium ions. In fact, although the analysis of the extraction data of these ions from sodium nitrate solutions confirms the formation of [Th(TOPO) ₃ ⁴⁺ ](NO₃ ^?)₄ species in dichloromethane, the extraction of these ions into the ionic liquid was not affected by the presence of TOPO. This latter outcome states the process takes place by a cation-exchange mechanism. It is found that the extraction of thorium ions diminishes in the presence of nitric acid. Interestingly, in contrast to the results observed in the extraction of thorium ions from sodium nitrate solutions, TOPO shows a co-operative effect on the extraction of these ions from nitric acid media. This allows considering the mechanism of the extraction of Th⁴⁺ ions from nitric acid media as a mixed ion exchange-solvation mechanisms by formation of [Th(TOPO)⁴⁺](NO₃ ^?)(PF₆ ^?)₃ species.     

Cobalt complex in a room temperature ionic liquid: A convenient recyclable reagent for catalytic epoxidation of cyclic alkenes

Co-catalyzed epoxidation of cyclic alkenes proceeds in ionic liquid media (1-ethyl-3-methylimidazolium hexafluorophosphate). Epoxidation of the alkenes to respective epoxides was greatly accelerated by the use of a cobalt-based catalyst in the presence of H₂O₂ as an oxidant. The catalyst in ionic liquid [Emim]PF₆ was recycled and reused for about seven times.     

Speciation of mercury by ionic liquid-based single-drop microextraction combined with high-performance liquid chromatography-photodiode array detection

Room temperature ionic liquids can be considered as environmentally benign solvents with unique physicochemical properties. Ionic liquids can be used as extractant phases in SDME, being compatible with chromatographic systems. A single-drop microextraction method was developed for separation and preconcentration of mercury species (MeHg⁺, EtHg⁺, PhHg⁺ and Hg²⁺), which relies on the formation of the corresponding dithizonates and microextraction of these neutral chelates onto a microdrop of an ionic liquid. Afterwards, the separation and determination were carried out by high-performance liquid chromatography with a photodiode array detector. Variables affecting the formation and extraction of mercury dithizonates were optimized. The optimum conditions found were: microextraction time, 20 min; stirring rate, 900 rpm; pH, 11; ionic liquid type, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]); drop volume, 4 μL; and no sodium chloride addition. Limits of detection were between 1.0 and 22.8 μg L⁻¹ for the four species of mercury, while the repeatability of the method, expressed as relative standard deviation, was between 3.7 and 11.6% (n = 8). The method was finally applied to the determination of mercury species in different water samples.     

Ionic liquids extraction of Para Red and Sudan dyes from chilli powder, chilli oil and food additive combined with high performance liquid chromatography

A simple analytical method, based on the coupling of ionic liquid-based extraction with high performance liquid chromatography (HPLC), is developed for the determination of Sudan dyes (I, II, III and IV) and Para Red in chilli powder, chilli oil and food additive samples. Two ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim][PF₆]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈mim][PF₆]), were compared as extraction solvents; experiments indicated that the latter possesses higher recoveries for each analyte. Parameters related to extraction of Sudan dyes and Para Red were also optimized. Under the optimal conditions, good reproducibility of extraction performance was obtained, with the relative standard deviation (RSD) values ranging from 2.0% to 3.5%. The detection limits of Sudan dyes and Para Red (LOD, S/N = 3) were in the range of 7.0-8.2 μg kg⁻¹ for chilli powder and 11.2-13.2 μg L⁻¹ for chilli oil and food additive. The recoveries were in the range of 76.8-109.5% for chilli powder samples and 70.7-107.8% for chilli oil and food additive samples.