Physical states of aqueous solutions of oxyethylated glycerol with polymerization degree of n=30 at temperatures lower than 283 K

A binary system water-oxyethylated glycerol with polymerization degree of n=30 (OEG(n=30)) is studied over the concentration range of 0-100% (w/w) and the temperature range of 123-283 K by differential scanning calorimetry (DSC). A phase diagram of this system is constructed at the average cooling rate of 200 K min(-1) and the warming rate of 0.5 K min(-1). Ice crystallization occurs and 70% (w/w) unfrozen residues remain during cooling in the OEG(n=30) concentration range of 0-45% (w/w). The system hardens in the amorphous state during cooling and ice crystallization occurs during warming in the range of 46-62% (w/w). Crystallization is observed neither during the cooling nor the subsequent warming in the range of 63-74% (w/w). OEG(n=30) crystallization occurs in the range of 75-100% (w/w). Each OEG(n=30) molecule can strongly bind to 48 water molecules. In parallel with DSC study, the water-OEG(n=30) system is investigated by cryornicroscopy in the temperature range of 173-283 K. Cryomicrographs of the solidified solutions representing each of the four concentration bands mentioned above are given.