Peculiar Nonideal Behavior of Deeply Supercooled Equimolar Binary Mixture of Water and Ethylene Glycol: DSC, Densitometry, and Rheology Study

An equimolar binary mixture of water and ethylene glycol (EWEGM) exhibits an atypical thermodynamic behavior, i.e. , regular crystallization at − 43 °C occurs only when the sample is properly seeded; otherwise, a glass transition (T g ) is observed at − 123 °C even at cooling rates as low as 0.1 K min⁻ 1 , as revealed through our DSC measurements. No crystallization was detected when the sample was subjected to mechanical stress by forcing it to flow through a capillary viscometer at − 75 °C. The addition of 0.3 M (NH 4 ) 2 SO 4 , or 3 mM Al(OH) 3 , or 1 mM AgI, in the form of nanocrystals, to EWEGM does not promote the crystallization on cooling either. The density of EWEGM exceeds that of the ideal mixture (defined as the weighted linear combination of the densities of pure water and ethylene glycol) throughout the explored temperature range (+ 40 to − 75 °C), consistent with the measured negative enthalpy of mixing (Δ mix H = − 16.6 ± 0.3 J g⁻ 1 ). The isobaric heat capacity was measured from + 20 to − 150 °C and was found to exceed the ideal value by 6 % in the temperature interval 0 to + 20 °C. The viscosity of EWEGM shows a pronounced deviation from Arrhenius behavior across the entire temperature interval investigated (+ 40 to − 115 °C); EWEGM can be classified as a moderately fragile liquid ( m = 70). The relationship ln( η / η ₀) = f(T) is accurately captured by the VFT model, and the resulting parameters are discussed in detail. In addition, mode‑coupling theory and the Adam–Gibbs model were applied to obtain deeper insight into the temperature dependence of the mixture’s peculiar thermophysical properties, and the corresponding analysis is included as well.