Vibrational spectroscopic study on cold crystallization of water in aqueous PEG solution

It has been reported that the water in aqueous PEG solution freezes at ca. -40 °C upon heating from lower temperature, ca. -100 °C, thus, such a water is called Cold-Crystallizable Water (CCW). In this study, the structure of CCW in PEG-DME-water system was examined by FT-IR. CCW was observed at a high cooling rate (120 K/hour) at ca. 223 K upon heating, whereas not at a low cooling rate (30 K/hour). These results indicate that anomalous water such as CCW may not exist at room temperature. Furthermore, spectral changes at ca. 223 K where CCW occurs indicate that dimeric water associated with PEG chain crystallize at that temperature.