## 2 Materials and Methods  
This work is based on an analysis of the kinetic criterion of glass transition in amorphous polymers and chalcogenide glasses As-S, Se-Ge, and As-Se. It is known that when a glass-forming liquid is cooled at temperatures in the region of the glass transition temperature, the viscosity of substances increases sharply. Conventionally, the liquid-glass transition (i.e., vitrification) occurs when the viscosity reaches \(\eta_{g}=\eta(T_{g})\), where  
\[\eta_{g}\approx const\approx 10^{12}\;\mathrm{Pa}\cdot\mathrm{s} \tag{1}\]  
Relation (1) is an approximate rule for the constancy of the logarithm of viscosity at the glass transition temperature \(T_{g}\), i.e., this relation (1) can be considered as a logarithmical approximate phenomenological criterion for glass transition [9]. [PERSON] [10] states that, for most of the studied glasses, the value of \(T_{g}\) corresponds to temperatures at which the viscosity \(\eta_{g}\) takes values in the range from \(10^{11}\) to \(10^{12}\) Pa\(\cdot\mathrm{s}\), and its value fluctuates in the region of the approximate value (1) with some scatter. However, this is not always the case, as can be seen from Table 4 of Ref. [11], which reveals that the actual viscosities at glass transition temperatures vary from \(10^{8.8}\) to \(10^{13}\) Pa\(\cdot\mathrm{s}\), which is far different from arbitrarily agreed viscosity (1). The constancy of \(log(\eta_{g})\) is better fulfilled for glassy systems of the same class [10]. In the scientific literature, it is also generally accepted that the liquid-glass transition for amorphous substances, including the studied polymers, occurs at viscosity values \(\eta(T_{g})\) in the range of \(10^{12}\)-\(10^{13}\) Pa\(\cdot\mathrm{s}\)[10]. Attempts were made to determine the temperature dependence of the viscosity of amorphous substances using the Arrhenius equation, but they were unsuccessful in view of the fact that the activation energy of a viscous flow in the region of the glass transition temperature depends on temperature and can be determined only in a narrow temperature range [10; 12]. For simple low-viscosity liquids, the Frenkel equation is used for the temperature dependence of viscosity [1; 2; 3; 13]:  
\[\eta=\eta_{0}\exp\left(\frac{U}{RT}\right) \tag{2}\]  
where the activation energy \(U\) is taken as a constant value, and \(\eta_{0}\) is the high-temperature viscosity limit [14]. However, as mentioned above, for glass-forming melts, the activation energy of viscous flow in the glass transition region depends quite noticeably on the temperature \(U=U(T)\). In this regard, the scientific community considers it most successful in determining the temperature dependence of the viscosity of amorphous materials, including polymers using the Williams-Landel-Ferry (WLF) equation [1; 2; 3; 15; 16; 17]:  
\[\ln a_{T}=-C_{1}\frac{T-T_{g}}{T-T_{g}+C_{2}},\;a_{T}=\frac{\eta(T)}{\eta\left( T_{g}\right)}\cong\frac{\tau(T)}{\tau\left(T_{g}\right)}, \tag{3}\]  
where \(a_{T}\) is the relative viscosity, and \(\tau\) is the structural relaxation time. The values of the parameters of the WLF equation \(C_{1}\) and \(C_{2}\) and some characteristics of the glass transition process calculated on their basis for various chalcogenide glasses and polymers are shown in Table 1[5; 18]. At the same time, \(C_{1}\) in Equation (3) is, in the first approximation, a universal constant for various classes of amorphous substances, including the studied polymers. It is noteworthy that the WLF equation is practically equivalent to the Vogel-Fulcher-Tammann (VFT) equation:  
\[\eta(T)=A\cdot\exp\left[\frac{B}{T-T_{0}}\right], \tag{4}\]  
while substituting \(B=C_{1}(T-T_{g})\), \(T_{0}=T_{g}-C_{2}\). It is worth noting that we are using the WLF empirical equation to identify the temperature interval where different liquids transform into glasses because the activation energy of flow starts changing, namely, at \(T_{g}\) (see, e.g., [19] and Figures 1, 2 and 4 of [20]).