A General Methodology to Predict the Linear Rheology of Branched Polymers

Abstract

We present a general coarse-grained model for predicting the linear viscoelasic properties of branched polymers from the knowledge of their molecular structure and three viscoelastic parameters, i.e., the Rouse time of an entanglement segment, the plateau modulus, and the entanglement molecular weight. The model uses the ingredients of the tube-based theories of McLeish and co-workers, and its implementation is based on a time-marching algorithm; this conceptual approach was already successfully applied to linear and star polymers, and it is appropriately modified here to account for more complex branched architectures, within the framework of dynamic tube dilation (using the criteria of Graessley). Whereas the molecular physics behind this model is the well-established hierarchical tube-based motion, the new element is a different macromolecular coordinate system and account of the branch points diffusion. With proper account of polydispersity, successful description of a wide range of rheological data of H and pompom polymers is obtained, with the use of the dilution exponent α = 1 and the parameter p2 = 1. The proposed methodology thus represents a generic approach for predicting the linear rheology of branched polymers.