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Miscibility of ionic liquids with polyhydric alcohols
Anna Makowska1, Ewa Dyoniziak, Agnieszka Siporska
1Faculty of Chemistry, University of Warsaw, Zwirki i Wigury 101, 02-089 Warsaw, Poland. milew@chem.uw.edu.pl
The Journal of Physical Chemistry. B
|January 26, 2010
Summary
Ionic liquids and polyhydric alcohols show upper critical solution temperatures. Miscibility depends on the ionic liquid anion
Area of Science:
- Physical Chemistry
- Materials Science
- Chemical Engineering
Background:
- Ionic liquids (ILs) and polyhydric alcohols are versatile chemical compounds with unique properties.
- Understanding liquid-liquid miscibility is crucial for designing separation processes and novel materials.
- The interplay between IL structure and alcohol properties influences their phase behavior.
Purpose of the Study:
- To experimentally determine liquid-liquid miscibility temperatures for binary systems of ILs and polyhydric alcohols.
- To investigate the influence of IL anion nature, cation alkyl chain length, and alcohol structure on miscibility.
- To elucidate the relationship between IL miscibility and anion hydrogen-bond acceptor strength.
Main Methods:
- Experimental determination of miscibility temperatures as a function of composition.
- Systematic variation of ionic liquid anions ([BF(4)](-), [PF(6)](-), [Tf(2)N](-)) and cations ([emim](+), [bmim](+), [hmim](+)).
- Systematic variation of polyhydric alcohols (diols and triols) with different hydroxyl group numbers and positions.
Main Results:
- All investigated systems exhibited upper critical solution temperatures (UCSTs).
- For dihydroxy alcohols, IL miscibility followed the order [BF(4)](-) > [Tf(2)N](-) > [PF(6)](-), correlating with anion hydrogen-bond basicity.
- The order of critical temperatures for 1,2-ethanediol with varying alkyl chain lengths ([emim](+) < [bmim](+) < [hmim](+)) was opposite to that observed with monohydroxy alcohols.
Conclusions:
- The miscibility of ionic liquids with polyhydric alcohols is strongly influenced by the hydrogen-bond acceptor strength of the IL anion.
- Increasing alcohol polarity generally decreases miscibility with specific ILs like [bmim][Tf(2)N] and [bmim][BF(4)].
- The observed trends highlight the complex structure-property relationships governing IL-polyol phase behavior.
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