Cooperativity, Relaxation and Irreversible Thermodynamics

A model for the intermolecular cooperative motion of the molecular segments (conformers) for the relaxation is proposed. As with the theory of Adam and Gibbs, the domain size for cooperativity is shown to be inversely proportional to the conformational entropy, and it grows larger as the temperature is lowered. The apparent activation energy for the mean relaxation time is predicted to be proportional to the critical domain size, and this result is in quantitative agreement with the Vogel-Fulcher and WLF equations.