A MOLECULAR-MODEL FOR COOPERATIVE LOCAL MOTIONS IN AMORPHOUS POLYMERS

A simple molecular model has been proposed for rotational motions of simple molecules in liquids and for local segmental motions in condensed polymer systems. In order to describe the behavior of cooperative segmental motions, we consider a model in which gears are rotating synchronously. The gear model predicts that the number of cooperatively moving segments increases with decreasing temperature and diverges at a critical temperature, T0. Thus the relaxation time also diverges at T0 as given empirically by the Vogel equation. This model as well explains the nonexponential correlation function given by the Kohlrausch-Williams-Watts equation and the diluent effect on the relaxation time. © 1990, American Chemical Society. All rights reserved.