Judging from the outside

Oeiras, 02.08.11

Surface tension is what makes soap bubbles possible. But it is also a very useful property to characterize liquids. In particular, surface tension can be used to understand the unique nature of ionic liquids and ionic liquids-containing solutions. ITQB researchers from the Lab of Molecular Thermodynamics and co-workers made a critical assessment of the available results on this property and published their conclusions in Chemical Society Reviews.

Ionic liquids are best described as liquid salts that do not evaporate easily. Their constituting ions, somewhat bulkier and asymmetrical than those of common salt, can be paired in many combinations to make an almost infinite array of liquids with uncommon properties and exciting applications. But their special nature provides special challenges to their characterization ‒ and this is where surface tension comes in.

In practice, one measures how the liquid’s surface, when ideally exposed to vacuum, resists to an external force. Surface tension values vary with both the nature of the liquid and temperature, and, for mixtures, they constitute a precious indication of how ionic liquids interact with other substances. At the limit, these values help on predicting several other properties at conditions beyond experimental range; then, one can profitably use this information to tailor a specific ionic liquid on demand.

Original Article

Chem. Soc. Rev., 2012, Advance Article DOI: 10.1039/C1CS15146K

Surface tension of ionic liquids and ionic liquid solutions

Mohammad Tariq, Mara G. Freire, Benilde Saramago, João A. P. Coutinho, José N. Canongia Lopes and Luís Paulo N. Rebelo

Chemical Society Reviews publishes accessible, succinct and reader-friendly articles on topics of current interest in the chemical sciences. Impact Factor 26.6 (2010)