Lower Critical Solution Temperature in the Metastable Region of an Ionic Solution in a Non-Polar Solvent

Dittmar, Harro; Schröer, Wolffram

doi:10.1021/jp8103485

Cited by 14 publications

(15 citation statements)

References 54 publications

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“…For (T * ,c)-diagrams in Fig. 3 (b), one can see the closed miscibility loops and the lower critical solution points (LCSP), the existence of which was also observed experimentally in [62] for ionic solutions in a non-polar solvent (the solution of N 4444 Br in toluene). However, it was shown in [62] that the phase transition related to the LCSP is located in a metastable region.…”

Section: Phase Diagrams Of the Rpm-hs Mixturesupporting

confidence: 64%

Phase behaviour in ionic solutions: Restricted primitive model of ionic liquid in explicit neutral solvent

Patsahan

2019

Journal of Molecular Liquids

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We study fluid-fluid equilibrium in the simplest model of ionic solutions where the solvent is explicitly included, i.e., a binary mixture consisting of a restricted primitive model (RPM) and neutral hard-spheres (RPM-HS mixture). First, using the collective variable method we find free energy, pressure and partial chemical potentials in the random phase approximation (RPA) for a rather general model that takes into consideration solvent-solvent and solvent-ion interactions beyond the hard core. In the special case of a RPM-HS mixture, we consider two regularizations of the Coulomb potential inside the hard core, i.e., the Weeks-Chandler-Andersen (WCA) regularization leading to the WCA approximation and the optimized regularization giving the optimized RPA (ORPA) or the mean spherical approximation (MSA). Furthermore, we calculate the phase coexistence using the associative mean spherical approximation (AMSA). In general, the three approximations produce qualitatively similar phase diagrams of the RPM-HS mixture, i.e., a fluid-fluid coexistence envelope with an upper critical solution point, a shift of the coexistence region towards higher total number densities and higher solvent concentrations with increasing pressure, and a small increase of the critical temperature with an increase of pressure. As for a pure RPM, the AMSA leads to the best agreement with the available simulation data when the association constant proposed by Olaussen and Stell is used. We also discuss the peculiarities of the phase diagrams in the WCA approximation. , η RP M c , and P RP M c are the critical temperature, the critical packing fraction, and the critical pressure of a pure RPM fluid, respectively. T * , η, and c are defined in Eq. (32), and P * = P εσ 4 /q 2 .

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Section: Phase Diagrams Of the Rpm-hs Mixturesupporting

confidence: 64%

Phase behaviour in ionic solutions: Restricted primitive model of ionic liquid in explicit neutral solvent

Patsahan

2019

Journal of Molecular Liquids

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“…Systematic screening experiments for solutions of salts explore phase diagrams in the full range of solvents from non-polar hydrocarbons to water, the most polar solvent considered till now. Phase diagrams of solutions in linear [79], cyclic and [80] aromatic hydrocarbons [81][82][83][84], alcohols [85][86][87][88][89] and water [87] have been discovered and investigated in some detail. The ionic liquids, considered mostly, contain an imidazolium cation [80][81][82][85][86][87], but ionic liquids with phosphonium [79] or ammonium cations [83,84] [80,81,85,86].…”

Section: Experiments Determining the Nature Of The Critical Pointmentioning

confidence: 99%

“…Phase diagrams of solutions in linear [79], cyclic and [80] aromatic hydrocarbons [81][82][83][84], alcohols [85][86][87][88][89] and water [87] have been discovered and investigated in some detail. The ionic liquids, considered mostly, contain an imidazolium cation [80][81][82][85][86][87], but ionic liquids with phosphonium [79] or ammonium cations [83,84] [80,81,85,86]. Figure 3 shows www.cpp-journal.org as example of a typical ionic liquid the structure of Butyl-methyl-imidazolium bis(trifluormethyl sulfonyl)imide (C 4 mim(CF 3 SO 2 ) 2 N) Most phase diagrams show an upper critical solution point as expected from simulations of the RPM, but phase diagrams with a lower critical solution point [23,90], closed solubility loop [84] and more complicated phase diagrams [81] have been observed as well.…”

Section: Experiments Determining the Nature Of The Critical Pointmentioning

confidence: 99%

“…The ionic liquids, considered mostly, contain an imidazolium cation [80][81][82][85][86][87], but ionic liquids with phosphonium [79] or ammonium cations [83,84] [80,81,85,86]. Figure 3 shows www.cpp-journal.org as example of a typical ionic liquid the structure of Butyl-methyl-imidazolium bis(trifluormethyl sulfonyl)imide (C 4 mim(CF 3 SO 2 ) 2 N) Most phase diagrams show an upper critical solution point as expected from simulations of the RPM, but phase diagrams with a lower critical solution point [23,90], closed solubility loop [84] and more complicated phase diagrams [81] have been observed as well. In order to get some overview the data of the phase diagrams are expressed by the variables of the RPM.…”

Section: Experiments Determining the Nature Of The Critical Pointmentioning

confidence: 99%

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A Short History of Phase Transitions in Ionic Fluids

Schröer

2012

Contrib. Plasma Phys.

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The paper reviews the development of theory and experiments concerning the nature of the critical point in ionic fluids. Because of the long-range nature of the Coulomb interactions the possibility of mean-field critical behaviour was discussed as a possibility. Although some experiments supported mean-field criticality, simulations on the model fluid of charged hard spheres and later experiments on ionic solutions have shown that phase transition of ionic systems belong to the Ising universality class like phase transitions in non-ionic fluids. Experiments concerning the crossover from Ising to mean field-behaviour are discussed as well as systematic differences between the phase behaviour predicted for the model fluid of charged hard spheres and that observed in ionic solutions.

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“…There are a few reports of the LCST-type phase transition of mixtures containing alkylammonium salts and molecular liquids. [18][19][20][21][22] Seddon et al reported that IL/chloroalkane [23] and IL/aromatic hydrocarbon [24] mixtures exhibited both UCST and LCST behaviour. We recently reported that ILs containing amino acid anions with a trifluoromethanesulfonyl group on the amino group and alkylphosphonium cations underwent a clear phase separation with water at room temperature; the homogeneous phase was obtained upon cooling.…”

Section: Introductionmentioning

confidence: 99%

Material design of ionic liquids to show temperature-sensitive LCST-type phase transition after mixing with water

et al. 2011

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Phosphonium cations bearing different alkyl chains were coupled with several common anions so as to prepare ionic liquids (ILs) with diverse hydrophobicity. A temperature-driven phase behaviour of the mixture of various ILs and water has been examined. A few ILs were found to exhibit temperature-sensitive lower critical solution temperature (LCST)-type phase transition after mixing with water. The phase separation temperature (T c ) of the IL/water mixtures depended strongly on the hydrophobicity of the component ions as well as mixing ratio. The number of water molecules per ion pair in the IL phase (m water ) increased dramatically upon cooling. The temperature dependence of this parameter was found to be useful to predict the possibility of the ILs to show the LCST-type phase behaviour after mixing with water. Since the value of m water depended on the ion structure, especially on the hydrophobicity, the T c was accurately set out by suitably mixing two ILs with different hydrophobicity.

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Lower Critical Solution Temperature in the Metastable Region of an Ionic Solution in a Non-Polar Solvent

Cited by 14 publications

References 54 publications

Phase behaviour in ionic solutions: Restricted primitive model of ionic liquid in explicit neutral solvent

Phase behaviour in ionic solutions: Restricted primitive model of ionic liquid in explicit neutral solvent

A Short History of Phase Transitions in Ionic Fluids

Material design of ionic liquids to show temperature-sensitive LCST-type phase transition after mixing with water

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