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 (OEGn=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-1 per min and the warming rate of 0.5 K-1 per min. Ice crystallization occurs and 70% (w/w) unfrozen residues remain during cooling in the OEGn=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). OEGn=30 crystallization occurs in the range of 75-100% (w/w). Each OEGn=30 molecule can strongly bind to 48 water molecules. In parallel with dsc study, the water-OEGn=30 system is investigated by cryomicroscopy in the temperature range of 173-283 K. Cryomicrographs of the solidified solutions representing each of the four concentration bands mentioned above are given.