Entropy theory of glass

II. Strengths and Weakness of the Original Entropy Theories of Glass Formation... 

Martinez and Angell [4] have recently reviewed the parallelism between the temperature dependence of the viscosity and that of S, and they have shown that this correlation is strong for the small molecule glass formers considered in their study. Since these findings are relevant to the entropy theory of glass formation. 

II. STRENGTHS AND WEAKNESSES OF THE ORIGINAL ENTROPY THEORIES OF GLASS FORMATION... 

As mentioned in the introduction, the vanishing of and the corresponding divergence of r in the entropy theory of glass formation appear upon... 

An obvious shortcoming of the entropy theory of glass formation is the fact that is not directly measurable. Section VI describes how the relative specific... 

From these values, one may calculate and compare the effective glass transition temperature of the resin as a function of diluent concentration. Gordon et a1. have recently derived an expression relating the glass temperature of a polymer-plasticizer mixture to the glass temperatures of the components on the basis of the configurational entropy theory of glass formation (4). 

One must be carefiil here because one can prove too much. The entropy theory of glasses, also called the Gibbs-Di Marzio (GD) theory, is a theory of equilibrium thermodynamic quantities only, it is not a theory of the kinetics of glasses. Polymer viscosities do in fact get so large at the glass transition that the relaxation times in the material equal and exceed the time scale of the experiment. At such temperatures one should not expect to have a perfect prediction of the various thermodynamic quantities. It is sensible to suppose that our predictions should not accord perfectly with experiment in these high viscosity regions. 

Thus, at a reduced temperature (To/Tm) of approximately 0.45 the viscosity of non-Arrhenian oxide liquids tend to infinity. Caillot et al. [3] have also shown that the viscosity of a variety of liquids diverge at a reduced temperature of 0.5. This behavior is predicted by both free-volume and entropy theories of glass transition [1]. 

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