AN INVESTIGATION OF THE PARAMETERS OF THE VTF EQUATION IN POLYHYDRIC ALCOHOLS AND THEIR AQUEOUS SOLUTIONS

DEWEY LANDON SMITH, Purdue University

Abstract

The impending entropy catastrophe of the Kauzmann paradox can be resolved by the imposition of a second order transition at a non - zero temperature. At the postulated transition temperature the liquid has lost the mobility but retained the long range disorder that characterizes the liquid at higher temperature. The empirical VTF equation also suggests the existance of a temperature at which a liquid losses its mobility. The polyhydric alcohols are shown to have a structural relaxation time temperature dependence that allows comparison of the entropy based transition temperature to the temperature at which the VTF equation predicts an infinitely long relaxation time for the liquid. A series of measurements on the polyhydric alcohols establishes the equivalence of the two transition temperatures within the experimental uncertainty of the measurement. The VTF parameters for aqueous solutions of polyhydric alcohols have been determined over a range of compositions from dielectric measurements. With VTF parameters determined from literature viscosity measurements, a qualitative prediction of the relationship between the B parameter of the VTF equation and the difference in the heat capacity between the liquid and the glass is observed. At high water concentrations, water's anomalously high heat capacity is seen to lead to an artificially high T(,0). A secondary relaxation in sorbitol is observed and a possible mechanism to account for the relaxation is suggested.

Degree

Ph.D.

Subject Area

Chemistry

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