Dielectric properties of normal supercooled water obtained in alcohol/water mixtures

The complex permittivity of (alcohol)_x/(water)_1-x mixtures was studied between 1 mHz and 10 MHz, from ambient down to the glass transition temperature, in the molar fraction range 0.1⩽x⩽1. Using methanol, ethanol, propanediol 1-2, and propanetriol 1-2-3 as the second component at sufficiently high concentration (x⩾0.1) eliminates the anomalous properties of pure water, and further explorations at x=0 lead to the normal part of static permittivity and relaxation time of supercooled water down to its glass transition temperature T_g=-135°C. These calculated values are nearly independent of the alcohol used. The static permittivity between +100 and -135°C can be adjusted by the relation ∈_s=-22.2+29950/T, which agrees well with the random network model. The dielectric relaxation time can be fitted to the free-volume percolation model of M.H. Cohen and G.S. Grest (1984). As long as the solutions remain homogeneous, dielectric spectra exhibit a single absorption peak, which broadens near the glass transition temperature