Ionic Clusters vs. Shear Viscosity in Aqueous Amino Acid Ionic Liquids

TL;DR

This study uses molecular dynamics simulations to explore how cluster formations in amino acid ionic liquid solutions relate to shear viscosity, providing insights for designing better AAILs for biochemical applications.

Contribution

First to establish simple correlations between cluster composition and viscosity in aqueous amino acid ionic liquids using molecular dynamics simulations.

Findings

Identified correlations between cluster size and viscosity.

Demonstrated that knowledge of one property can predict the other.

Analyzed effects of amino acid structure on solution properties.

Abstract

Aqueous solutions of amino acid ionic liquids (AAILs) are of high importance for applications in protein synthesis and solubilization, enzymatic reactions, templates for synthetic study, etc. This work employs molecular dynamics simulations using our own force field to investigate shear viscosity and cluster compositions of three 1-ethyl-3-methylimidazolium (emim) amino acid salts: [emim][ala], [emim][met], and [emim][trp] solutions (2, 5, 10, 20, 30 mol%) in water at 310 K. We, for the first time, establish simple correlations between cluster composition, on one side, and viscosity, on another side. We argue that knowledge about any of these properties alone is enough to derive insights regarding the missed properties, using the reported correlations. The numerical observations and qualitative correlations are discussed in the context of chemical structure of the amino acid anions, [ala], [met], and [trp]. The reported results will enhance progress in the efficient design and applications of AAILs and their solutions.