Predictions and Verifications of Universal Cooperative Relaxation and Diffusion in Materials

Abstract

Since its inception in 1979 the Coupling Model has predictions on the dynamic properties of relaxation and diffusion that should be universal in materials with many-body interactions. The verifications of this bold prediction require the studies of many different relaxation and diffusion processes in diverse kinds of material. These tasks performed over the past four decades have culminated in the overwhelming confirmation of the predictions as reported in the extensive review by the author published in Prog. Mater. Sci., 139, 101130 (2023). A large variety of relaxation and diffusion processes in widely different classes of materials are shown to have the predicted universal properties. In particular for polymers, the local segmental relaxation responsible for glass transition conforms to the universal properties. However, not known is whether diffusion of the entangled chains in high molecular weight polymers also follows the same or not. In this paper, published data of diffusion of entangled polymer chains from experiments and simulations are reexamined and reevaluated to show indeed that they are in conformity with the universal properties. The same conclusion holds also for diffusion and rheology of entangled cyclic polymers. This paper is written as a tribute to C. Michael Roland for his scientific collaborations and camaraderie with the author over many years.