The Dynamics of the Glass Transition

Accepting the widely held view that all glass transitions have the same features, a particularly simple model of a liquid of long rod molecules is studied. It is shown that the equations of motion of such a system are remarkably simple and permit simple intuitive pictures of the glass transition to be translated into a theoretical model for molecular diffusivity. The calculation derives the Vogel–Fulcher–Dolittle law which is shown to stem from the co-operative motion of molecules being the only survivor near Tg. Right at Tg it is shown that a power law replaces V–F–D. An analysis is also given of the time relaxation of the system, the Kohlrausch–Williams–Watts law. This however is not critically related to the V–F–D structure, but follows from the averaging over a spectrum of relaxation times.