Pressure dependence of the glass transition temperature in ionic liquids and solutions. Evidence against free volume theories

E. Williams, Charles Angell

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48 Citations (Scopus)

Abstract

A simple DTA method of determining the glass transition temperature, Tg, of a supercooled liquid using small samples under high pressure has been developed and applied to the study of several anhydrous ionic liquid binary systems, and salt + water systems. Values of the pressure dependence of Tg have been compared with those predicted (a) from the pressure dependence of electrical conductance and (b) from the changes of heat capacity and expansion coefficient observed at Tg by use of the quasi-thermodynamic relation dTg/dP = TgVgΔα/ΔCp. In the case of alkali acetate + water systems, Tg is almost independent of pressure, and, in the case of the composition LiOAc·10 H2O, dTg/dP is actually negative. This result, which implies a decrease in expansion coefficient on increase of temperature through the glass transition, is conceptually incompatible with a free volume interpretation of liquid relaxational properties.

Original languageEnglish (US)
Pages (from-to)232-237
Number of pages6
JournalJournal of Physical Chemistry
Volume81
Issue number3
StatePublished - 1977
Externally publishedYes

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Ionic Liquids
Free volume
Ionic liquids
pressure dependence
glass transition temperature
liquids
expansion
coefficients
water
Saline water
acetates
alkalies
thermal analysis
Liquids
Alkalies
specific heat
Differential thermal analysis
Specific heat
salts
Glass transition

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

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abstract = "A simple DTA method of determining the glass transition temperature, Tg, of a supercooled liquid using small samples under high pressure has been developed and applied to the study of several anhydrous ionic liquid binary systems, and salt + water systems. Values of the pressure dependence of Tg have been compared with those predicted (a) from the pressure dependence of electrical conductance and (b) from the changes of heat capacity and expansion coefficient observed at Tg by use of the quasi-thermodynamic relation dTg/dP = TgVgΔα/ΔCp. In the case of alkali acetate + water systems, Tg is almost independent of pressure, and, in the case of the composition LiOAc·10 H2O, dTg/dP is actually negative. This result, which implies a decrease in expansion coefficient on increase of temperature through the glass transition, is conceptually incompatible with a free volume interpretation of liquid relaxational properties.",
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T1 - Pressure dependence of the glass transition temperature in ionic liquids and solutions. Evidence against free volume theories

AU - Williams, E.

AU - Angell, Charles

PY - 1977

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N2 - A simple DTA method of determining the glass transition temperature, Tg, of a supercooled liquid using small samples under high pressure has been developed and applied to the study of several anhydrous ionic liquid binary systems, and salt + water systems. Values of the pressure dependence of Tg have been compared with those predicted (a) from the pressure dependence of electrical conductance and (b) from the changes of heat capacity and expansion coefficient observed at Tg by use of the quasi-thermodynamic relation dTg/dP = TgVgΔα/ΔCp. In the case of alkali acetate + water systems, Tg is almost independent of pressure, and, in the case of the composition LiOAc·10 H2O, dTg/dP is actually negative. This result, which implies a decrease in expansion coefficient on increase of temperature through the glass transition, is conceptually incompatible with a free volume interpretation of liquid relaxational properties.

AB - A simple DTA method of determining the glass transition temperature, Tg, of a supercooled liquid using small samples under high pressure has been developed and applied to the study of several anhydrous ionic liquid binary systems, and salt + water systems. Values of the pressure dependence of Tg have been compared with those predicted (a) from the pressure dependence of electrical conductance and (b) from the changes of heat capacity and expansion coefficient observed at Tg by use of the quasi-thermodynamic relation dTg/dP = TgVgΔα/ΔCp. In the case of alkali acetate + water systems, Tg is almost independent of pressure, and, in the case of the composition LiOAc·10 H2O, dTg/dP is actually negative. This result, which implies a decrease in expansion coefficient on increase of temperature through the glass transition, is conceptually incompatible with a free volume interpretation of liquid relaxational properties.

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