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Structural heterogeneities in ionic liquids and their relation to solvent and mechanical properties

Mercredi 20 janvier 2016 11:00 - Duree : 1 heure
Lieu : Science Building - Room 401, 4th floor - ESRF - 71 avenue des Martyrs - Grenoble

Orateur : Arno A. VELDHORST (University of Sao Paulo, Brazil)

Ionic liquids containing 1-alkyl-3-methylimidazolium cations are known for their complicated structure at the nanoscale. Depending on the length of the alkyl chain of the cation, the non-polar alkyl chains may form separate domains from the polar network containing the charged parts of the ions. The talk will contain two different studies related to these nanoscale heterogeneities.

The first part is related to the peculiar ability of ionic liquids to dissolve both polar and non-polar substances. Quantities which aim to predict this ability, e.g., the cohesive energy and the internal pressure, fail to give good estimates of solubilities for ionic liquids. By calculating the cohesive energy density and internal pressure separately for the different domains in the liquids, we find that these quantities do agree with common solvents locally.

The other part is related to the boson peak, which is seen in glasses as an excess in the low-frequency vibrational density of states (compared to the Debye model, which describes the density of states of crystals). Recent theoretical explanations of the boson peak relate it to heterogeneity of the mechanical properties in glasses. In ionic liquids however, the boson peak seems to be independent of the nature of the (structural) heterogeneities. Our aim is thus to get a better understanding of the local mechanical properties of the ionic liquids.

Contact : taffut@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Site de l'évènement : Polygone scientifique

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