On the molecular mobility in amorphous polymers, inorganic glasses, and amorphous metal alloys in the glass transition range

Abstract

The transition of kinetic units (atoms or groups of atoms) in amorphous media from one quasi-equilibrium state to another is determined by fluctuations of both energy and entropy of the system. In the glass transition range of liquids and polymers, the entropic mechanism plays a determining role: the fluctuation of packing of particles turns out to be more important than accumulation of energy. Above the glass transition range, the energy mechanism begins to play a dominant role. The procedure that is currently used to calculate the constant for the Bartenev equation, which relates the relaxation time to the cooling rate at the glass transition temperature, leads to overestimated values. A procedure for the calculation of this parameter was proposed with allowance for the temperature dependence of the entropy of activation in the region of the liquid-glass transition. The use of this equation in the relaxation spectrometry of amorphous polymers, inorganic glasses, and amorphous metal alloys is discussed.