Experimental analysis of deep eutectic solvents to derive fundamental correlations between local parent species properties and bulk material properties utilizing differential scanning calorimetry

Deep eutectic solvents (DESs) are a newer class of solvents with the potential to substitute for conventional organic solvents used in a wide variety of chemical processing applications, including separations, syntheses, and red-ox flow electrochemical cell units, among others. These solvents offer benefits over traditional organic solvents such as lower health hazards, lower environmental impacts, higher sustainability, ease of preparation, and the ability to meet very specific design specifications. The appeal of DESs is their ability to serve as designer solvents. However, there is a lack of predictive models which accurately characterize the thermophysical properties of the mixtures. This work focuses on developing a fundamental understanding of how local structures of parent species may be used to predict and correlate to bulk material properties of corresponding mixtures. Experimental data has been collected for binary DES mixtures of choline halide salts with ethylene glycol, glycerol, and urea using differential scanning calorimetry. Applications of constant-ratio DSC testing has been utilized to assess trends in glass transition temperature as a function of heating a cooling rate, in efforts to determine true transition temperatures. Coupling of experimental data and ideal solution theory has provided insights to begin developing predictive models for deep eutectic solvent design.