DESs form by complexion of quaternary ammonium salt (usually choline chloride) together with a hydrogen bond donor (HBD). The formation of hydrogen bonding between the halide anion of choline chloride and functional groups of hydrogen-donor agent is responsible for the decrease in the freezing point of DESs in relation to the melting points of the individual components Low cost, high purity, chemical inertness with water, easy preparation and environmental friendliness.
