(592f) Molecular Dynamics Simulation of Binary and Ternary Deep Eutectic Solvents

Authors: 
Benjamin, K. M., South Dakota School of Mines and Technology
Raynie, D., South Dakota State University
Solvent use is of great importance to chemical and biological industries. Solvents are crucial to several processing steps, including reaction, separation, and stabilization. In several instances, the types of conventional organic solvents used are both potentially toxic to an individual, as well as to the environment. As an alternative, deep eutectic solvents (DES) are biologically based ionic liquid eutectic mixtures which possess tunable properties according to the selected cation, anion, and hydrogen bond donating co-solvent partner. These tunable properties include density, dielectric constant, and solvating power. DES possess extremely low vapor pressures, and therefore do not volatilize as easily as conventional organic solvents used in the pharmaceutical industry. Moreover, because DES are comprised of biologically based ions (i.e. choline) rather than synthetic ions (i.e. 1-ethyl-3-methyl-imidazolium), they are less toxic to organisms and the environment, and less expensive.

This work seeks to characterize environmentally benign, non-toxic, tunable DES through a combination of experimentation and molecular modeling and simulation. In particular, molecular dynamics (MD) simulations are used to compute densities, coefficients of thermal expansion, and Hildebrand solubility parameters for various binary and ternary DES, comprised of mixtures of choline chloride, urea, and glycerol. Simulation predictions of density compare well to experimental measurements. In addition, radial distribution functions (RDF) are computed to interpret the local fluid structure. RDF analysis highlights several interesting comparisons (based on composition) between urea and glycerol as hydrogen bond donors (interacting with choline and chloride) within DES, as well as unique hydrogen bonding between urea and glycerol molecules within the DES mixture.

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