How sensitive are physical properties of choline chloride–urea mixtures to composition changes: Molecular dynamics simulations and Kirkwood–Buff theory

Deep eutectic solvents (DESs) have emerged as a cheaper and greener alternative to conventional organic solvents. Choline chloride (ChCl) mixed with urea at molar ratio of 1:2 is one the most common DESs for wide range applications such electrochemistry, material science, biochemistry. In this study, molecular dynamics simulations are performed study effect content on thermodynamic transport properties ChCl mixtures. With increased mole fraction urea, number hydrogen bonds (HBs) between cation–anion ion–urea decreases, while HBs urea–urea increases. Radial distribution functions (RDFs) ChCl–urea ChCl–ChCl pairs shows significant decrease Using computed RDFs, Kirkwood–Buff Integrals (KBIs) computed. KBIs show that interactions become stronger, urea–ChCl slightly weaker increasing urea. All factors found larger than one, indicating non-ideal mixture. Our results also self- collective diffusivities increase, viscosities content. This mainly due ions resulting in enhanced mobilities. Ionic conductivities exhibit non-monotonic behavior. Up 0.5, ionic increase then reach plateau.