Linear Viscoelasticity

Abstract

The linear viscoelasticity of a polymer is uniquely described by the classical theory of linear viscoelasticity. Material properties are contained in the relaxation time spectrum which depends on the molecular details. To address an unsolved problem in rheology, the search for relations between molecular architecture and relaxation, we propose to start out with the most simple molecular architecture and later add molecular details. This proposal bases on the observation that polymers with the mostt simple geometry (long linear flexible chains of uniform length) relax with a universal relaxation time spectrum which is self-similar. Its parameters are a generic expression of chain flexibility, rotational energies of the chemical bonds, atomic masses involved in the molecular motion, molecular interaction forces, etc. of the chemical building blocks. We assume that these generic parameters can be considered fixed for each chemistry and that only few new parameters have to be added when proceeding to architectures which are branched or distributed in size (polydisperse). In a similar fashion one may add specific effects of solvents, molecular interactions, or phase transition (not elaborated here). Generic parameters are given for polystyrene, a polybutadiene, and a polyvinylmethylether.