Dielectric study of the α and β processes in supercooled ethylene glycol oligomer–water mixtures

Broadband dielectric measurements for 65 wt % ethylene glycol oligomer (EGO)–water mixtures with one to six repeat units of EGO molecules were performed in the frequency range of 10 μHz–10 GHz and the temperature range of 128–298 K. In the case of the water-EGO mixtures with one and two repeat units of the EGO molecule (small EGO), the shape of the dielectric loss peak of the primary process is asymmetrical about the logarithm of the frequency of maximum loss above the crossover temperature, TC. The asymmetric process continues to the α process at a low frequency, and an additional β process appears in the frequency range higher than that of the α process below TC. In contrast, the water-EGO mixtures with three or more repeat units of the EGO molecule (large EGO) show a broad and symmetrical loss peak of the primary process above TC. The symmetric process continues to the β process, and an additional α process appears in the frequency range lower than that of the β process below TC. These different scenar...