Vapor pressures of 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with long alkyl chains

Rocha, Marisa A.A.; Coutinho, João A. P.; Santos, Luı́s M. N. B. F.

doi:10.1063/1.4896704

Cited by 41 publications

(29 citation statements)

References 65 publications

(64 reference statements)

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“…The increase in ξ/d from ∼ 0.7 at n = 8 to ∼ 1.3 at n = 22 reflects an increase in the number of layers and a concomitant reduction of the surface entropy, demonstrating the n-increasing dominance of the chain-segregating vdW interaction. This conclusion agrees with the conclusion of bulk RTIL vaporization enthalpy studies (43,52,53), where the increase in the enthalpy with n is fully due to the increase in the vdW contribution. The Coulomb contribution remains constant, or even decreases slightly, rendering the vdW contribution at large n twice or more larger than the Coulomb one (52-54).…”

Section: Resultssupporting

confidence: 91%

Surface structure evolution in a homologous series of ionic liquids

Haddad

Pontoni

Murphy

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Interfaces of room temperature ionic liquids (RTILs) are important for both applications and basic science and are therefore intensely studied. However, the evolution of their interface structure with the cation's alkyl chain length [Formula: see text] from Coulomb to van der Waals interaction domination has not yet been studied for even a single broad homologous RTIL series. We present here such a study of the liquid-air interface for [Formula: see text], using angstrom-resolution X-ray methods. For [Formula: see text], a typical "simple liquid" monotonic surface-normal electron density profile [Formula: see text] is obtained, like those of water and organic solvents. For [Formula: see text], increasingly more pronounced nanoscale self-segregation of the molecules' charged moieties and apolar chains yields surface layering with alternating regions of headgroups and chains. The layering decays into the bulk over a few, to a few tens, of nanometers. The layering periods and decay lengths, their linear [Formula: see text] dependence, and slopes are discussed within two models, one with partial-chain interdigitation and the other with liquid-like chains. No surface-parallel long-range order is found within the surface layer. For [Formula: see text], a different surface phase is observed above melting. Our results also impact general liquid-phase issues like supramolecular self-aggregation and bulk-surface structure relations.

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Section: Resultssupporting

confidence: 91%

Surface structure evolution in a homologous series of ionic liquids

Haddad

Pontoni

Murphy

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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“…Moreover, this macroscopic segregation behaviour has been shown to be a major feature in the ionic liquid bulk phase and as reflected in the thermophysical properties of ILs. [66][67][68][69][70][71][72][73] Similar trend shifts were observed in the IL viscosity, [66][67] surface tension, 68 vapour pressure, 69,70 heat capacity, 71 among others. 72,73 It is, however, thought-provoking to highlight that different trends on the IL acidity with increasing alkyl chain length have also been reported.…”

Section: Experimental Kamlet-taft Solvatochromic Parameterssupporting

confidence: 70%

Hydrogen-bond acidity of ionic liquids: an extended scale

Kurnia

Lima

Cláudio

et al. 2015

Phys. Chem. Chem. Phys.

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One of the main drawbacks comprising an appropriate selection of ionic liquids (ILs) for a target application is related to the lack of an extended and well-established polarity scale for these neoteric fluids. Albeit considerable progress has been made on identifying chemical structures and factors that influence the polarity of ILs, there still exists a high inconsistency in the experimental values reported by different authors. Furthermore, due to the extremely large number of possible ILs that can be synthesized, the experimental characterization of their polarity is a major limitation when envisaging the choice of an IL with a desired polarity. Therefore, it is of crucial relevance to develop correlation schemes and a priori predictive methods able to forecast the polarity of new (or not yet synthesized) fluids. In this context, and aiming at broadening the experimental polarity scale available for ILs, the solvatochromic Kamlet-Taft parameters of a broad range of bis(trifluoromethylsulfonyl)imide-([NTf 2 ] − )-based fluids were determined. The impact of the IL cation structure on the hydrogen-bond donating ability of the fluid was comprehensively addressed. Based on the large amount of novel experimental values obtained, we then evaluated COSMO-RS, COnductor-like Screening MOdel for Real Solvents, as an alternative tool to estimate the hydrogen-bond acidity of ILs. A three-parameter model based on the cation-anion interaction energies was found to adequately describe the experimental hydrogen-bond acidity or hydrogen-bond donating ability of ILs. The proposed three-parameter model is also shown to present a predictive capacity and to provide novel molecular-level insights into the chemical structure characteristics that influence the acidity of a given IL. It is shown that although the equimolar cation-anion hydrogen-bonding energies (E HB ) play the major role, the electrostaticmisfit interactions (E MF ) and van der Waals forces (E vdW ) also contribute, admittedly in a lower extent, towards the hydrogen-bond acidity of ILs. The new extended scale provided for the hydrogen-bond acidity of ILs is of high value for the design of new ILs for task-specific applications. † Electronic supplementary information (ESI) available: Comparison between experimental and literature solvatochromic values; correlation between experimental and predicted hydrogen-bond acidity; equation to calculate the absolute relative deviation. See

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“…The trend shift at the critical alkyl size n = 6 reported earlier [12] for the enthalpies and entropies of vaporization is confirmed by the present results (figure 10). The break at n = 6 was observed previously in the surface tension and viscosity [24], [25] and in other properties [26], [27], [28], [29]. To provide better detection of the trend change, the complete alkyl series from n = (1 to 10) including odd and even number of carbons were used.…”

Section: Resultsmentioning

confidence: 98%

Thermodynamics of long-chain 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids

Paulechka

Blokhin

Rodrigues

et al. 2016

The Journal of Chemical Thermodynamics

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The heat capacities in the temperature range (5 to 370) K and the parameters of solid-phase phase transitions and fusion were determined for three [Cnmim][NTf2] (n = 10, 14, 16) ILs. The temperature-dependent vapour pressures of [C14mim][NTf2] and [C16mim][NTf2] were measured with a Knudsen effusion apparatus combined with a quartz crystal microbalance. Thermodynamic properties of these compounds in the crystal, liquid, and gas states were derived from the obtained data. The results obtained in this work were combined to those available in the literature for the short-chain homologues to discuss regularities in thermodynamic properties of the series. While some properties demonstrate simple linear dependence on the alkyl chain length, a more complicated behaviour with strong nonlinearity or a break at n = 6 is observed for others.

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Vapor pressures of 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with long alkyl chains

Cited by 41 publications

References 65 publications

Surface structure evolution in a homologous series of ionic liquids

Surface structure evolution in a homologous series of ionic liquids

Hydrogen-bond acidity of ionic liquids: an extended scale

Thermodynamics of long-chain 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids

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