On the relaxation nature of the glass transition of amorphous polymers and low-molecular amorphous materials

The relative temperature range $(\delta T_g/T_g)$ characterizing the liquid-to-glass transition is a single-valued function of the fluctuation volume fraction $f_g$ frozen at the glass transition temperature $T_g$. The fluctuation volume $\Delta V_e$ of the amorphous material is determined by delocalization of active (excited)) atoms, i.e., their thermal displacements from equilibrium positions. The fluctuation volume fraction $f=\Delta V_e/V$ controls the molecular mobility that is characteristic of delocalized atoms in the liquid-glass transition region. It is shown that $\delta T_g$ for the majority of amorphous materials is only 0.7% of the glass transition temperature $T_g$. The narrow temperature range $\delta T_g$ is consistent with the classical Simon concept on the insignificant temperature range in which the structure is frozen.