Interactions Of Ionic Liquids With Solutes, Particles And Surfaces: Insights From Molecular Simulation And Experimental Thermodynamics

Abstract:

Room-temperature molten salts, or ionic liquids, are complex fluids. In order to be fluid around room temperature, the ions composing them must be bulky, asymmetric, flexible, with delocalized electrostatic charge, or contain non-polar moieties. Combinations of some or all of these factors are usual. This variety of features leads to diverse physical-chemical properties, the understanding of which requires a description of the molecular interactions taking place in bulk ionic liquids, when solutes are solvated in them, or when they are in presence of mesoscopic objects such as colloidal particles and macroscopic surfaces. Molecular interaction models can be used to provide structural and energetic information about ionic liquid systems, and help design new compounds for applications in chemical processes, devices and materials. An important effort has been put into accurately describing molecular interactions of ionic liquids, starting from ion-ion interactions, ion-solute interactions (where the solute is a molecular compound) and leading to ion-surface interactions including glass or metallic surfaces. The methodologies used are quantum chemical calculations and molecular simulation.These methods provide insight into the local order of the ionic liquid phases and into the dominant energetic terms, allowing us to investigate how an ionic liquid is organized at the molecular scale, to elucidate important questions regarding the dominant contributions within the interactions, and to put in evidence the mechanisms of solvation of different compounds.Illustrative applications include ionic liquids tailored for the capture of CO2, biodegradable ionic liquids, new media for hydrogenation catalysis using metallic nanoparticles, and the friction properties of ionic liquids at metal surfaces in the context of the development of novel ionic lubricants.

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