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The multiple phases (and faces) of Ionic Liquids

By: Jose Nuno Canongia Lopes
From: Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Centro de Quimica Estrutural, Instituto Superior Tecnico
At: Complexo Interdisciplinar, Anfiteatro
[2009-02-25] 12:00

Ionic liquids are generally described as salts with melting temperatures below 100ºC, negligible vapor pressures and liquids interesting solvation properties. In this presentation we analyze these features from a molecular thermodynamics perspective. The discovery that ionic liquids can be distilled at low pressure and high temperature changed the belief that ionic liquids never occurred in the gas phase. Although their status as an important branch of green chemistry was not affected by this fact, new challenges lie on the characterization of such phase. Studies in this area corroborated the idea of ionic liquids as nano-segregated fluids, previously investigated by Molecular Dynamics (MD). On the other hand, the complex liquid-liquid and solid-liquid phase behavior of ionic liquids mixtures is illustrated by their phase diagrams: for example, (1-ethyl-3-methylimidazolium bistriflamide + aromatic molecule) systems sometimes show the existence of congruent­melting inclusion crystals. Selective interactions between aromatic compounds and the cation and anion of the ionic liquid can explain such behavior. Such analyses can be extended to other systems using other experimental techniques or MD simulation.