Molecular dynamic study of alcohol-based deep eutectic solvents

Abstract

The applicability of deep eutectic solvents is determined by their physicochemical properties. In turn, the properties of eutectic mixtures are the result of the components’ molar ratio and chemical composition. Owing to the relatively low viscosities displayed by alcohol-based deep eutectic solvents (DESs), their application in industry is more appealing. Modeling the composition–property relationships established in polyalcohol-based mixtures is crucial for both understanding and predicting their behavior. In this work, a physicochemical property–structure comparison study is made between four choline chloride polyalcohol-based DESs, namely, ethaline, propeline, propaneline, and glyceline. Physicochemical properties obtained from molecular dynamic simulations are compared to experimental data, whenever possible. The simulations cover the temperature range from 298.15 to 348.15 K. The simulated and literature experimental data are generally in good agreement for all the studied DESs. Structural properties, such as radial and spatial distribution functions, coordination numbers, hydrogen bond donor (HBD)–HBD aggregate formation, and hydrogen bonding are analyzed in detail. The higher prevalence of HBD:HBD and HBD:anion hydrogen bonds is likely to be the major reason for the relatively high density and viscosity of glyceline as well as for lower DES self-diffusions.

Computer Simulations of Deep Eutectic Solvents: Challenges, Solutions, and Perspectives

“…Most of the works on the structures of classical DESs are based on ChCl, such as reline [ 64 , 70 , 76 , 123 , 208 , 209 , 210 , 211 , 212 ] (HBD is urea), ethaline [ 161 , 210 , 213 , 214 ] (HBD is ethylene glycol), glyceline [ 82 , 210 , 215 ] (HBD is glycerol), and propoline [ 216 , 217 ] (HBD is propylene glycol). Over the last five years, their structures and properties have been investigated intensively and the main interactions have been determined.…”

“…Glyceline also exhibits over-saturation of HBD groups, which leads to higher cohesive forces within the bulk liquid and to a higher viscosity than ethaline due to more extensive interactions between HBDs. Another comparison of the choline-based DESs was performed by Ferreira et al [ 216 , 217 ]. In their first work [ 216 ], they developed a non-polarizable OPLS-based FF for propeline.…”

“…The results showed that the HBDs in propeline have a preference to interact with the salt rather than with itself, which explains its relatively high viscosity. In the follow-up work Ferreira et al [ 217 ] compared four DESs, namely, ethaline, propeline, propaneline (based on propanediol), and glyceline. Glyceline, which has a higher number of hydroxyl groups, demonstrated a higher degree of H-bonding formation with the anion.…”

Simulation of deep eutectic solvents: Progress to promises

“…114,127,128 Refinement of FF parameters have meant that subsequent classical simulations have continued to improve in the prediction and reproduction of DES physical properties, including density, surface tension, heat capacity, and viscosity. 105,108,113,[129][130][131][132][133][134] Solvent organization can also be easily derived from bulk-phase MD simulations. For example, computed center-of-mass radial distribution functions (RDFs) by Sun et al revealed that the long-range ordering of intercalating cations and anions in neat ChCl diminished with increasing concentration of urea molecules in CCU.…”

“…The earliest reported MD simulations of DESs came a decade after their initial discovery 114,127,128 . Refinement of FF parameters have meant that subsequent classical simulations have continued to improve in the prediction and reproduction of DES physical properties, including density, surface tension, heat capacity, and viscosity 105,108,113,129–134 . Solvent organization can also be easily derived from bulk‐phase MD simulations.…”