Acetone as a Polar Cosolvent for Pyridinium-Based Ionic Liquids

TL;DR

This study investigates how acetone as a polar cosolvent affects the transport and structural properties of pyridinium-based ionic liquids, revealing enhanced conductivity and diffusivity in their mixtures.

Contribution

It provides new insights into the effects of acetone on ionic liquids' properties, highlighting their potential as effective co-solvents for improved performance.

Findings

Maximum ionic conductivity at 10 mol% RTIL in mixtures

[BPY][TF] exhibits higher ionic conductivity due to weaker cation-anion binding

Acetone significantly reduces viscosity and enhances diffusivity

Abstract

The work reports transport and structure properties of the three pyridinium-based ionic liquids (RTILs) - N-butylpyridinium hexafluorophosphate [BPY][PF6], N-butylpyridinium trifluorosulfonate [BPY][TF] and N-butylpyridinium bis(trifluoromethanesulfonyl)imide [BPY][TFSI] - in their mixtures with acetone (ACET). The ionic conductivity maximum occurs at 10 mol% RTIL, irrespective of the anion. The absolute ionic conductivity value of [BPY][TF] is higher than those of other RTILs. This is explained by a weaker cation-anion binding than that in [BPY][PF6] and smaller anion size than that of [BPY][TFSI]. All the investigated RTILs are infinitely miscible with ACET, which boosts their diffusivity and conductivity. A small viscosity of ACET favors a drastic viscosity decay in the RTIL-ACET mixtures. Structure analysis (radial distribution functions, ionic clusters) of the mixtures are in line with their transport properties providing a reliable microscopic interpretation of the observed macroscopic properties. As a molecular co-solvent, ACET constitutes an interesting alternative and competitor to more intensively investigated liquids.