Mesostructure and physical properties of aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl sulfate doped with divalent sulfate salts in the liquid and the mesomorphic states

Oscar Cabeza, Luisa Segade, Montserrat Domínguez-Pérez, Esther Rilo, David Ausín, Anna Martinelli, Negin Yaghini, Bernhard Gollas, Manfred Kriechbaum, Olga Russina, Alessandro Triolo, Elena López-Lago, Luis M Varela

Research output: Contribution to journalArticleResearchpeer-review

Abstract

This paper extends the study of the induced temperature change in the mesostructure and in the physical properties occurring in aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl-sulfate [EMIm][OSO4]. For some compositions, these mixtures undergo a phase transition between the liquid (isotropic in the mesoscale) and the mesomorphic state (lyotropic liquid crystalline) at about room temperature. The behavior of mixtures doped with a divalent metal sulfate was investigated in order to observe their applicability as electrolytes. Calcium sulfate salt is almost insoluble even in the 20 wt% water mixture. The magnesium salt, in contrast, can be dissolved up to concentrations of 730 ppm in the same mixture and it has a profound impact on its properties. Six aqueous mixtures (with water content from 10 wt% to 33 wt%) of [EMIm][OSO4] were saturated with magnesium sulfate salt, producing the ternary mixture [EMIm][OSO4] + H2O + MgSO4. Viscosity, density and ionic conductivity for these samples were measured from 10 °C to 90 °C. In addition, SAXS, FTIR, diffussion NMR and Raman spectroscopy of the most interesting samples have been performed, and structural data indicate a transition between a hexagonal lyotropic liquid crystalline phase below and an isotropic solution phase above room temperature. The octyl sulfate anions of the cylindrical micelles in the hexagonal phase are coordinated with water molecules through H-bonds (about four per sulfate anion), while the [EMIm] cations seem to be poorly coordinated and so free to move. Inorganic salt addition reinforces that network, increasing the phase transition temperature.

Original languageEnglish
Pages (from-to)8724-8736
Number of pages13
JournalPhysical chemistry, chemical physics
Volume20
Issue number13
DOIs
Publication statusPublished - 28 Mar 2018

Fingerprint

Ionic Liquids
Sulfates
sulfates
Physical properties
Salts
physical properties
salts
Liquids
liquids
Anions
Phase transitions
magnesium sulfates
Crystalline materials
anions
Calcium Sulfate
Magnesium Sulfate
conductivity
Water
Micelles
room temperature

Keywords

  • Journal Article

Fields of Expertise

  • Advanced Materials Science

Cite this

Mesostructure and physical properties of aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl sulfate doped with divalent sulfate salts in the liquid and the mesomorphic states. / Cabeza, Oscar; Segade, Luisa; Domínguez-Pérez, Montserrat; Rilo, Esther; Ausín, David; Martinelli, Anna; Yaghini, Negin; Gollas, Bernhard; Kriechbaum, Manfred; Russina, Olga; Triolo, Alessandro; López-Lago, Elena; Varela, Luis M.

In: Physical chemistry, chemical physics, Vol. 20, No. 13, 28.03.2018, p. 8724-8736.

Research output: Contribution to journalArticleResearchpeer-review

Cabeza, Oscar ; Segade, Luisa ; Domínguez-Pérez, Montserrat ; Rilo, Esther ; Ausín, David ; Martinelli, Anna ; Yaghini, Negin ; Gollas, Bernhard ; Kriechbaum, Manfred ; Russina, Olga ; Triolo, Alessandro ; López-Lago, Elena ; Varela, Luis M. / Mesostructure and physical properties of aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl sulfate doped with divalent sulfate salts in the liquid and the mesomorphic states. In: Physical chemistry, chemical physics. 2018 ; Vol. 20, No. 13. pp. 8724-8736.
@article{a505fcc5d15a43d8a7fe68f8aab48606,
title = "Mesostructure and physical properties of aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl sulfate doped with divalent sulfate salts in the liquid and the mesomorphic states",
abstract = "This paper extends the study of the induced temperature change in the mesostructure and in the physical properties occurring in aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl-sulfate [EMIm][OSO4]. For some compositions, these mixtures undergo a phase transition between the liquid (isotropic in the mesoscale) and the mesomorphic state (lyotropic liquid crystalline) at about room temperature. The behavior of mixtures doped with a divalent metal sulfate was investigated in order to observe their applicability as electrolytes. Calcium sulfate salt is almost insoluble even in the 20 wt{\%} water mixture. The magnesium salt, in contrast, can be dissolved up to concentrations of 730 ppm in the same mixture and it has a profound impact on its properties. Six aqueous mixtures (with water content from 10 wt{\%} to 33 wt{\%}) of [EMIm][OSO4] were saturated with magnesium sulfate salt, producing the ternary mixture [EMIm][OSO4] + H2O + MgSO4. Viscosity, density and ionic conductivity for these samples were measured from 10 °C to 90 °C. In addition, SAXS, FTIR, diffussion NMR and Raman spectroscopy of the most interesting samples have been performed, and structural data indicate a transition between a hexagonal lyotropic liquid crystalline phase below and an isotropic solution phase above room temperature. The octyl sulfate anions of the cylindrical micelles in the hexagonal phase are coordinated with water molecules through H-bonds (about four per sulfate anion), while the [EMIm] cations seem to be poorly coordinated and so free to move. Inorganic salt addition reinforces that network, increasing the phase transition temperature.",
keywords = "Journal Article",
author = "Oscar Cabeza and Luisa Segade and Montserrat Dom{\'i}nguez-P{\'e}rez and Esther Rilo and David Aus{\'i}n and Anna Martinelli and Negin Yaghini and Bernhard Gollas and Manfred Kriechbaum and Olga Russina and Alessandro Triolo and Elena L{\'o}pez-Lago and Varela, {Luis M}",
year = "2018",
month = "3",
day = "28",
doi = "10.1039/c7cp07999k",
language = "English",
volume = "20",
pages = "8724--8736",
journal = "Physical chemistry, chemical physics",
issn = "1463-9076",
publisher = "Royal Society of Chemistry",
number = "13",

}

TY - JOUR

T1 - Mesostructure and physical properties of aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl sulfate doped with divalent sulfate salts in the liquid and the mesomorphic states

AU - Cabeza, Oscar

AU - Segade, Luisa

AU - Domínguez-Pérez, Montserrat

AU - Rilo, Esther

AU - Ausín, David

AU - Martinelli, Anna

AU - Yaghini, Negin

AU - Gollas, Bernhard

AU - Kriechbaum, Manfred

AU - Russina, Olga

AU - Triolo, Alessandro

AU - López-Lago, Elena

AU - Varela, Luis M

PY - 2018/3/28

Y1 - 2018/3/28

N2 - This paper extends the study of the induced temperature change in the mesostructure and in the physical properties occurring in aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl-sulfate [EMIm][OSO4]. For some compositions, these mixtures undergo a phase transition between the liquid (isotropic in the mesoscale) and the mesomorphic state (lyotropic liquid crystalline) at about room temperature. The behavior of mixtures doped with a divalent metal sulfate was investigated in order to observe their applicability as electrolytes. Calcium sulfate salt is almost insoluble even in the 20 wt% water mixture. The magnesium salt, in contrast, can be dissolved up to concentrations of 730 ppm in the same mixture and it has a profound impact on its properties. Six aqueous mixtures (with water content from 10 wt% to 33 wt%) of [EMIm][OSO4] were saturated with magnesium sulfate salt, producing the ternary mixture [EMIm][OSO4] + H2O + MgSO4. Viscosity, density and ionic conductivity for these samples were measured from 10 °C to 90 °C. In addition, SAXS, FTIR, diffussion NMR and Raman spectroscopy of the most interesting samples have been performed, and structural data indicate a transition between a hexagonal lyotropic liquid crystalline phase below and an isotropic solution phase above room temperature. The octyl sulfate anions of the cylindrical micelles in the hexagonal phase are coordinated with water molecules through H-bonds (about four per sulfate anion), while the [EMIm] cations seem to be poorly coordinated and so free to move. Inorganic salt addition reinforces that network, increasing the phase transition temperature.

AB - This paper extends the study of the induced temperature change in the mesostructure and in the physical properties occurring in aqueous mixtures of the ionic liquid 1-ethyl-3-methyl imidazolium octyl-sulfate [EMIm][OSO4]. For some compositions, these mixtures undergo a phase transition between the liquid (isotropic in the mesoscale) and the mesomorphic state (lyotropic liquid crystalline) at about room temperature. The behavior of mixtures doped with a divalent metal sulfate was investigated in order to observe their applicability as electrolytes. Calcium sulfate salt is almost insoluble even in the 20 wt% water mixture. The magnesium salt, in contrast, can be dissolved up to concentrations of 730 ppm in the same mixture and it has a profound impact on its properties. Six aqueous mixtures (with water content from 10 wt% to 33 wt%) of [EMIm][OSO4] were saturated with magnesium sulfate salt, producing the ternary mixture [EMIm][OSO4] + H2O + MgSO4. Viscosity, density and ionic conductivity for these samples were measured from 10 °C to 90 °C. In addition, SAXS, FTIR, diffussion NMR and Raman spectroscopy of the most interesting samples have been performed, and structural data indicate a transition between a hexagonal lyotropic liquid crystalline phase below and an isotropic solution phase above room temperature. The octyl sulfate anions of the cylindrical micelles in the hexagonal phase are coordinated with water molecules through H-bonds (about four per sulfate anion), while the [EMIm] cations seem to be poorly coordinated and so free to move. Inorganic salt addition reinforces that network, increasing the phase transition temperature.

KW - Journal Article

U2 - 10.1039/c7cp07999k

DO - 10.1039/c7cp07999k

M3 - Article

VL - 20

SP - 8724

EP - 8736

JO - Physical chemistry, chemical physics

JF - Physical chemistry, chemical physics

SN - 1463-9076

IS - 13

ER -