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Applications of complementary experimental techniques to the characterization of the phase diagram of [C16mim][PF6] and [C14mim][PF6] (Articolo in rivista)

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Applications of complementary experimental techniques to the characterization of the phase diagram of [C16mim][PF6] and [C14mim][PF6] (Articolo in rivista) (literal)

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De Roche J. 1, Gordon C. M. 2, Imrie C. T. 3, Ingram M. D. 4, Kennedy A. R. 5, Lo Celso F. 6, Triolo A. 7 (2003)
Applications of complementary experimental techniques to the characterization of the phase diagram of [C16mim][PF6] and [C14mim][PF6]
in Chemistry of materials
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De Roche J. 1, Gordon C. M. 2, Imrie C. T. 3, Ingram M. D. 4, Kennedy A. R. 5, Lo Celso F. 6, Triolo A. 7 (literal)

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Impact Factor = 3.967 In this high-impact paper, we present interesting original results on the nature of the phase diagram of two imidazolium salts. Our study is based on a critcal comparison between the findings from a number of complementary experimental techniques such as Quasi Elastic Neutron Scattering, Small and Wide Angle X-ray scattering, DSC, conductivity and Raman spectroscopy. This complete and detailed investigation highlights the existence of new phases in these salts and provides the structural-dynamical basis for wider investigations of similar, industrial relevant, salts. (literal)

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A range of analytical techniques (DSC, conductivity measurement, Raman spectroscopy, small- and wide-angle X-ray diffraction (S-WAXS), quasi-elastic neutron scattering (QENS), and single-crystal X-ray diffraction) are applied to the characterization of the phase behaviour of the low-melting-point liquid crystalline salts 1-hexadecyl-3-methylimidazolium hexafluorophosphate ([C16mim][PF6]) and 1-methyl-3-tetradecylimidazolium hexafluorophosphate [C14mim][PF6]. This is the first time that QENS has been applied to the structural analysis of this type of ionic liquid crystal. For the first time in this class of salts, a low-temperature phase transition is identified, which is assigned to a crystal-crystal transition. Conductivity and QENS data for [C16mim][PF6] suggest that the higher-temperature crystalline phase (CII) has greatly increased freedom in its long alkyl chain and anion than the lower-temperature crystalline phase (CI). This conclusion is supported by single-crystal X-ray diffraction results for [C14mim][PF6]. In both crystalline phases, as well as in the higher-temperature mesophase, the structure maintains a monodispersed layer structure with interdigitated alkyl chains. The structure of the mesophase is confirmed as smectic A by the S-WAXS and Raman spectroscopy results. Detailed analysis suggests that in this phase the alkyl chains undergo complete conformational melting. (literal)

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1,4,5)Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, UK, 2,3) Department of Pure & Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK, 6) Dipartimento di Chimica Fisica, Universita` di Palermo, Viale delle Scienze, Parco DOrleans 2, I-90128 Palermo, Italy, 7) Istituto Processi Chimico-Fisici, Sezione di Messina - CNR, Via La Farina 237, 98123 Messina, Italy (literal)

Titolo

Applications of complementary experimental techniques to the characterization of the phase diagram of [C16mim][PF6] and [C14mim][PF6] (literal)

Abstract

A range of analytical techniques (DSC, conductivity measurement, Raman spectroscopy, small- and wide-angle X-ray diffraction (S-WAXS), quasi-elastic neutron scattering (QENS), and single-crystal X-ray diffraction) are applied to the characterization of the phase behaviour of the low-melting-point liquid crystalline salts 1-hexadecyl-3-methylimidazolium hexafluorophosphate ([C16mim][PF6]) and 1-methyl-3-tetradecylimidazolium hexafluorophosphate [C14mim][PF6]. This is the first time that QENS has been applied to the structural analysis of this type of ionic liquid crystal. For the first time in this class of salts, a low-temperature phase transition is identified, which is assigned to a crystal-crystal transition. Conductivity and QENS data for [C16mim][PF6] suggest that the higher-temperature crystalline phase (CII) has greatly increased freedom in its long alkyl chain and anion than the lower-temperature crystalline phase (CI). This conclusion is supported by single-crystal X-ray diffraction results for [C14mim][PF6]. In both crystalline phases, as well as in the higher-temperature mesophase, the structure maintains a monodispersed layer structure with interdigitated alkyl chains. The structure of the mesophase is confirmed as smectic A by the S-WAXS and Raman spectroscopy results. Detailed analysis suggests that in this phase the alkyl chains undergo complete conformational melting. (literal)

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