Dynamics of uncrystallized water in partially crystallized poly(ethylene glycol)-water mixtures studied by dielectric spectroscopy

作者：Miyara Masahiko; Takashima Ikeru; Sasaki Kaito; Kita Rio; Shinyashiki Naoki^*; Yagihara Shin

来源：Polymer Journal, 2017, 49(6): 511-518.

DOI：10.1038/pj.2017.15

The dielectric relaxation process of water has been investigated for a partially crystallized poly(ethylene glycol) (PEG)-water mixture with PEG concentrations of up to 50 wt% at temperatures between - 60 and 25 degrees C and over the frequency range of 1 MHz to 50 GHz. At subzero temperatures, most of the water is crystallized, and another portion of the water, uncrystallized water (UCW), remains in a liquid state with the polymer in an uncrystallized phase. The relaxation strength, triangle epsilon of UCW for all PEG-water mixtures increased abruptly because of the melting of the eutectic of PEG and water. The triangle epsilon of UCW for 10-40 wt% PEG-water mixtures increased again because of the melting of ice, whereas the 50 wt% PEG-water mixture did not show any additional increase in triangle epsilon because it did not contain enough water to form ice crystals. The relaxation time of UCW in PEG-water mixtures is smaller than those observed in other polymer-water mixtures. The local fluctuation of the PEG chain, which has a smaller relaxation time than those of other polymers in water mixtures, and the characteristic hydration structure around the PEG chain prevent the formation of ice crystals even for water with a small relaxation time.

• 出版日期2017-6