The polymer–polymorphoid nature of glass aging

Abstract The analysis of numerous experimental data carried out on the basis of concept of polymer–polymorphoid structure of glass and glass-forming liquid showed that the glass-forming substances are the copolymers of nano-fragments (polymorphoids) of the different polymorphic modifications (PMs) without translational symmetry (long-range order), but with short- and intermediate-range orders of the inherent PMs. An interconversion of various PM polymorphoids and a change of their concentration ratio (CRP) in the glass-forming liquids and glass under external impacts and time are the physicochemical essence of structure and property changes due to the relaxation process up to crystallization found in certain PMs. The CRP of the various PMs is the fundamental physicochemical characteristic and it is an integral internal parameter of the nonequilibrium thermodynamic system and so defines the structure and the various properties of individual chemical substances, including: volume, entropy, thermal expansion coefficient and other internal parameters. The processes and degree of aging glass change various properties of the glass, including a change of enthalpy, manifested in the exo- and endothermic effects observed in the DSC thermograms during the heating and cooling of the glass. The physicochemical essence of the aging process consists of the polymorphoid transformations of high temperature polymorphic modifications (HTPM) into polymorphoids of low temperature (LTPM) ones that result in the crystallization of substances under certain conditions.