Glass transition temperature theoretical treatment

Recently, alternative theoretical expressions have been developed by using classical thermodynamic treatments to describe the compositional dependence of the glass transition temperature in miscible blends and further extended also to the epoxywater systems 2S,27). The studies carried out on DGEBA epoxy resins of relatively low glass transition have shown that the plasticization induced by water sorption can be described by theoretical predictions given by ... 

There are many empirical correlations for the activation energy, as well as some theoretical treatments [19-21]. These treatments usually attempt to relate Ep to quantities such as the size of the penetrant molecule (usually expressed in terms of a penetrant diameter or the square of this diameter, and sometimes corrected for the penetrant shape if it deviates significantly from spherical), the glass transition temperature of the polymer, and whether the polymer is glassy or rubbery at the temperature of interest. The diffusivity and solubility components of the permeability are usually treated separately in such attempts, as described below. 

In the case of the glass transition, more complete experimental data are available, at least with respect to vinyl polymers. As will be discussed below, for certain types of structure a substantial effect of stereoregularity on the glass transition temperature, T, is found, and in addition a theoretical treatment is available which accounts for these effects. However, very little data is available with respect to the effect of stereoregularity on, for example, the configurational entropy S at T, on aC, the size of the heat capacity increment at T, 0 on other key thermodynamic parameters of the glassy state. ... 

After observing quite a few anomalous properties of optical transitions in glasses and attributing them to the dynamics of TLS [14], the tunneling model was adopted by Reinecke [15] to explain the low-temperature line widths of optical transitions in amorphous solids using the concept of spectral diffusion. This concept had originally been developed for the description of spin resonance experiments [16] and had already been applied to the theoretical treatment of the above mentioned ultrasonic properties of glasses [17]. Soon after this step, the possibility of a connection between thermal and optical properties of amorphous solids was supported by the observation of time dependence of spectral hole widths [18]. 

---