Dielectric study on α- and β-processes in supercooled diethyleneglycol– and pentaethyleneglycol–water mixtures

Broadband dielectric measurements on 65 wt% diethyleneglycol– and pentaethyleneglycol–water mixtures were performed in the frequency range of 10 μHz–10 GHz and in the temperature range of 128–273 K. The α- and β-relaxation processes observed in the lower temperature range merged in the higher temperature range. The relaxation curve for the diethyleneglycol–water mixture was asymmetric above the separation temperature, and continued to the lower frequency process below the separation temperature, and an additional relaxation process appeared at the higher frequency below the separation temperature. In contrast, the relaxation curve for the pentaethyleneglycol–water mixture is symmetric above the separation temperature. The relaxation process continued to a higher frequency process below the separation temperature, and another lower frequency relaxation process appeared. These results reflect the cooperative motion of water and solute molecules with different sizes for each mixture.