Thermorheological Complexity in Polymers and the Problem of the Glass Transition

A current focus in studies of the glass transition is the role of dynamic heterogeneities. Although these efforts may clarify the origin of the spectacular change in properties of liquids approaching vitrification, we point out that a seemingly related phenomenon, thermorheological complexity in polymers, must involve different mechanisms. In particular, as seen from consideration of various properties involving the chain dynamics, averaging over different length and time scales cannot offer a resolution to the problem of thermorheological complexity.