Surface Tensions of Bis(trifluoromethylsulfonyl)imide Anion-Based Ionic Liquids (original) (raw)
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Surface Tensions for the 1Alkyl3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids
Journal of Chemical and Engineering Data, 2008
This work addresses surface tension measurements of eight imidazolium-based ionic liquids (ILs) with the bis(trifluoromethylsulfonyl)imide, Tf 2 N, common anion, and their dependence with temperature, from (293 to 353) K, at atmospheric pressure. The set of selected ionic liquids was chosen to provide a detailed and comprehensive study of the influence of the cation alkyl chain length on the surface tensions of the ionic liquids based on the Tf 2 N anion. It is shown that, unlike other ionic liquids, the surface tensions of the Tf 2 N family do not have a linear decrease with the chain length. The surface thermodynamic functions such as surface entropy and enthalpy were derived from the temperature dependence of the surface tension, and their values indicate the importance of the surface ordering in ionic liquids. The use of the Guggenheim and Eötvos correlations for the estimation of the critical temperatures of ionic liquids is discussed, and the applicability of the Stefan rule to ionic liquids is analyzed.
Surface tensions of imidazolium based ionic liquids: Anion, cation, temperature and water effect
Journal of Colloid and Interface Science, 2007
This work addresses the experimental measurements of the surface tension of eight imidazolium based ionic liquids (ILs) and their dependence with the temperature (288-353 K) and water content. The set of selected ionic liquids was chosen to provide a comprehensive study of the influence of the cation alkyl chain length, the number of cation substitutions and the anion on the properties under study. The influence of water content in the surface tension was studied for several ILs as a function of the temperature as well as a function of water mole fraction, for the most hydrophobic IL investigated, [omim][PF 6 ], and one of the more hygroscopic IL, [bmim] [PF 6 ]. The surface thermodynamic functions such as surface entropy and enthalpy were derived from the temperature dependence of the surface tension values.
Density and Surface Tension of Ionic Liquids [H 2 N–C 2 mim][PF 6 ] and [H 2 N–C 3 mim][PF 6 ]
Journal of Chemical & Engineering Data, 2012
Two amino functionalized ionic liquids 1-(2-aminoethyl)-3-methylimidazolium hexafluorophosphate, [H 2 N−C 2 mim][PF 6 ], and 1-(3-aminopropyl)-3-methylimidazolium hexafluorophosphate, [H 2 N− C 3 mim][PF 6 ], were synthesized and characterized. The density and surface tension of these ionic liquids were measured from (293.15 to 343.15) K. Their values decreased with increasing temperature. The physical properties such as coefficient of thermal expansion, molecular volume, standard molar entropy, lattice energy, and molar enthalpy of vaporization were estimated using experimental data. The critical temperature of the ionic liquids was estimated using Eoẗvos equations. The values were then used to estimate the boiling temperature of the ionic liquids according to methods of Rebelo. The interstice model was used to predict the thermal expansion coefficient of the ionic liquids, α, and the result was in very good agreement with the experimental value. In addition, the parachor method was used to predict the physical properties of the ionic liquids [H 2 N−C n mim][PF 6 ] (n = 4, 5, 6).
Fluid Phase Equilibria, 2010
The surface tension and density of almost all members of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amides family, [C n mim][Ntf 2 ], with 2 ≤ n ≤ 14 were measured for the first time up to 532 K and 473 K, respectively. The large number of ionic liquids studied within this family and the broad interval of working temperature enabled us to show evidence for a thermodynamic anomaly in the thermal expansivity of these ionic liquids (minima in˛p versus T). The minima themselves have never been witnessed before. The data in this extended temperature range also permitted us to discuss the location of hypothetical normal boiling and critical points.
Journal of Solution Chemistry, 2014
New experimental surface tension data have been provided at 283.15, 298.15, 313.15 K and atmospheric pressure for binary mixtures of 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with the alcohols: methanol, ethanol, 1-propanol, 2-propanol, l-butanol and 1-pentanol. The experimental results show that the surface tensions of these mixtures depend systematically on the alkyl chain length of the ionic liquid and alcohol, composition and temperature. Surface tension changes on mixing have been calculated and adequately fitted by the Redlich-Kister polynomial equation. The adjustable parameters and the standard deviations between experimental and calculated values are reported.
Surface tension measurements of imidazolium-based ionic liquids at liquid–vapor equilibrium
Fluid Phase Equilibria, 2008
A series of high quality 1-alkyl-3-methylimidazolium-based ionic liquids are synthesized and used for studying their surface tension. The capillary rise method is used for measuring the surface tension of I − , Cl − , PF 6 − , and BF 4 − salts in the temperature range 298-393 K. The capillary apparatus is evacuated and sealed under vacuum. The experimental results show that surface tension of these compounds depend systematically on temperature.
2012
Ionic liquids have attracted a large amount of interest in the past few years. One approach to better understand their peculiar nature and characteristics is through the analysis of their surface properties. Some research has provided novel information on the organization of pure ionic liquids at the vapor−liquid interface; yet, a systematic study on the surface properties of mixtures of ionic liquids and their organization at the surface has not previously been carried out in the literature. This work reports, for the first time, a comprehensive analysis of the surface organization of mixtures of ionic liquids constituted by 1-alkyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C n mim]-[NTf 2 ]. The surface tension of mixtures composed of [C 4 mim][NTf 2 ] + [C n mim][NTf 2 ] (n = 1, 2, 5, 6, 8, and 10) was experimentally determined, at 298.2 K and atmospheric pressure, in the whole composition range. From the experimental data, the surface tension deviations and the relative Gibbs adsorption isotherms were estimated showing how the surface composition of an ionic liquid mixture differs from that of the liquid bulk and that the surface is enriched by the ionic liquid with the longest alkyl chain length. Finally, the soft-SAFT equation of state coupled with the density gradient theory (DGT) was used, for the first time, to successfully reproduce the surface tension experimental data of binary mixtures of ionic liquids using a molecular-based approach. In addition, the DGT was used to compute the density profiles of the two components across the interface, confirming the experimental results for the components distribution at the bulk and at the vapor−liquid interface.
Journal of Molecular Liquids, 2016
Statistical associating fluid theory for potential of variable range has been used to provide an accurate thermophysical properties for 26 imidazolium and pyridinium-based families of ionic liquids (ILs) with different cationic structures combined with [PF 6 ] − , [BF 4 ] − , [NTf 2 ] − , [Cl] − , [dca] − , [Triflate] − , [EtSO 4 ] − , [lactate] − , [C(CN) 3 ] − and [MeSO 4 ] − anions. An appropriate set of molecular parameters were obtained by means of fitting the model predictions to experimental liquid densities over a wide temperature and pressure ranges. The overall absolute average relative deviation (AARD) between the calculated and experimental liquid densities is 0.12% over a wide range of temperature and pressure from 283 to 472 K and 0.1-200 MPa. The reliability and physical significance of the parameters were tested by calculation of thermodynamic derivative properties including isobaric thermal expansivity and isothermal compressibility of ILs. Moreover, the interfacial surface tension of ILs was calculated by density gradient theory (DGT) coupled with the SAFT-VR model. The results are in excellent agreement with the available experimental data.
Journal of Chemical & Engineering Data, 2007
Presented are experimental densities and surface tensions of imidazolium-, quaternary ammonium-, and phosphonium-based room-temperature ionic liquids (RTILs) in the temperature range of (298 to 350) K. Densities of the RTILs decrease slightly with temperature in the studied range (298 to 333) K. At 298 K, the densities of the phosphonium-based RTILs ranged from (0.88 to 1.05) g‚cm-3 , while those of the ammonium-based RTILs ranged from (1.08 to 1.37) g‚cm-3. The volume expansivities of phosphonium and ammonium RTILs at 1 atm and 298 K are in the range of (5.5 to 6.5)‚10-4 K-1. Surface tension and temperature relationships were established using the van der Waals-Guggenheim equation, σ) E s (1-T/T c) n , where n ≈ 1, for the RTILs studied. The Macleod-Sugden-Wright (MSW) equation was used to correlate surface tension with the respective molar volume of the various RTILs. The developed equation can accurately correlate surface tension for this grouping of RTILs with a maximum estimated error of 0.15 % within the temperature ranges considered.
Density and Surface Tension of Ionic Liquids
The Journal of Physical Chemistry B, 2010
We measured the density and surface tension of 9 bis[(trifluoromethyl)sulfonyl]imide ([Tf 2 N]-)-based and 12 1-methyl-3-octylimidazolium ([C 8 C 1 Im] +)-based ionic liquids (ILs) with the vibrating tube and the pendant drop method, respectively. This comprehensive set of ILs was chosen to probe the influence of the cations and anions on density and surface tension. When the alkyl chain length in the [C n C 1 Im][Tf 2 N] series (n) 1, 2, 4, 6, 8, 10, 12) is increased, a decrease in density is observed. The surface tension initially also decreases but reaches a plateau for alkyl chain lengths greater than n) 8. Functionalizing the alkyl chains with ethylene glycol groups results in a higher density as well as a higher surface tension. For the dependence of density and surface tension on the chemical nature of the anion, relations are only found for subgroups of the studied ILs. Density and surface tension values are discussed with respect to intermolecular interactions and surface composition as determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The absence of nonvolatile surface-active contaminants was proven by ARXPS.