Understanding the Nanoscale Ordering of Ionic Liquids and Deep Eutectic Solvents for Enhanced Separation Performance

Ionic liquids (ILs) and deep eutectic solvents (DESs) have desirable properties, such as negligible vapor pressure, high thermal stability, and structural tunability and have been used in a number of separations processes, including chromatography. Due to their structure and composition, they are known to undergo ordering at the nanoscale which is expected to affect numerous separations processes, such as analyte mass transfer. This talk will discuss research efforts underway at Ames National Laboratory to understand the nanoscale structuring of these solvents and how nanodomain formation can be exploited in separations processes. The talk will present data from single molecule tracking and fluorescence correlation spectroscopy that reveals the size of nanodomains in a phosphonium-based ionic liquid and their temperature dependence. We will discuss how the nanodomains in ILs can be exploited to improve separation performance. The presentation will include several case studies including the development of median involving silver(I) ions that have been shown to be highly selective towards olefins in gas chromatography. We will discuss this complexation capability and how it can be modified through the use of ligands coordinated to silver(I) ion. We will also discuss ongoing efforts to understand analyte solvation in DESs and how chromatography can be used as a platform to guide the design of these fascinating solvents.