DIELECTRIC-PROPERTIES OF NORMAL SUPERCOOLED WATER OBTAINED IN ALCOHOL WATER MIXTURES

We studied the complex permittivity of (alcohol)x/(water)1-x mixtures between 1 mHz and 10 MHz, from ambient down to the glass transition temperature, in the molar fraction range 0.1 less-than-or-equal-to x less-than-or-equal-to 1. The addition of a suitable second component decreases and even eliminates, at sufficient concentration, the anomalies characteristic of pure water and allows, according to Oguni and Angell, to separate the 'normal' and the 'anomalous' parts of water's physical properties. Using methanol, ethanol, propanediol 1-2 and propanetriol 1-2-3 as second component at sufficiently high concentration (x greater-than-or-equal-to 0.1), one eliminates the anomalies of pure water and so our further extrapolations 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-degrees-C. These calculated values are nearly independent of the alcohol used. The static permittivity between + 100 and - 135-degrees-C can be adjusted by the relation epsilon(s) = - 22.2 + 29950/T, which is in quite remarkable agreement with the random network model of Sceats and Rice. The dielectric relaxation time can be fitted according to the new free-volume percolation model of Cohen and Grest. As long as the solutions remain homogeneous, dielectric spectra exhibit a single absorption peak, which is well fitted by the Havriliak and Negami relation and which is broadening near glass transition temperature.