Structure of Citric Acid-Glycerol Deep Eutectic Solvents

Deep eutectic solvents (DES) are an emerging group of tuneable green solvents, comprising of two or more components that form a H-bonded network. Most published studies have focussed on halogen containing systems, where halide ions are a major contributor to the structure, but the presence of halide ions can cause unwanted effects, such as the poisoning of catalysts. Here we aim to study the structure of a halogen-free DES based on citric acid and glycerol at molar ratios 1:2 and 1:4 citric acid to glycerol. Changing the ratio induces a change in physico-chemical properties such as melting temperature and viscosity, as well as the solubility of metal salts and surfactants, most noticeably non-ionic surfactants are not soluble in 1:4 but form micelles in 1:2 mixtures. Therefore we aim to study the structural differences between these halogen free DES at the two different molar ratios.