Phase Diagram of the Monoethanolamine–Dimethyl Sulfoxide System according to the Data of Differential Scanning Calorimetry

Abstract

The phase diagram of the monoethanolamine (MEA)–dimethyl sulfoxide (DMSO) system was studied by differential scanning calorimetry in the temperature ranges from +25 to –140°C and from –140 to +40°C. The obtained phase diagram is of the eutectic type (the melting point of the eutectic is –10°C at ~50 mol % DMSO) and is characterized by strong overcooling of the liquid phase and glass transition at about –120°C. The results of the investigation of the phase diagrams of the systems water (H₂O)–DMSO and ethylene glycol (EG)–DMSO were compared with the published data. The possibility of the strong overcooling of the liquid phase in the systems MEA–DMSO, EG–DMSO, and H₂O–DMSO and their tendency to glass transition are explained by the stability of the spatial networks of hydrogen bonds of the solvents.