Insights into the orientation and hydrogen bond influence on thermophysical and transport properties in choline-based deep eutectic solvents and methanol

Abstract

The search for new solvents which fulfil the needs of modern times has put the Deep eutectic solvents (DESs) in a leading role given their wide range of applications, versatility, low cost, and minimal environmental impact. For the above reason, it is critical to achieving predictive capabilities and the accurate description of their properties, both macroscopic and microscopic. In this work, DESs based on choline chloride as the hydrogen bond acceptor plus ethylene glycol and glycerol as hydrogen bond donors have been analysed in a mixture with methanol. Densities, excess volume and viscosity were determined by molecular dynamics and predicted by the perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS). Radial distribution functions and the number of hydrogen bonds derived from molecular simulations confirmed an anticipated bonding network within the liquid, with significant ordering interactions. When methanol is added to the eutectic solvent become incorporated into this structure as a second hydrogen bond donor. Methanol reduces the viscosity, but the eutectic solvents retain their characteristics. The analysis performed in this work could be a valuable feature of the new theory in developing more realistic models of the hydrogen-bonding interaction in deep eutectic solvents.