Molecular simulations of the long-time behaviour of entangled polymeric liquids by the primitive chain network model

A novel simulation method that can calculate the long-time response of polymeric liquids in the entangled state is described. The polymer chain is replaced by a sequence of subchains connecting consecutive entanglements, called the 'primitive' chain. Collectively, the primitive chains form a rubberlike network, the nodes of which are the entanglements. The dynamics is modelled separately in two parts: motion of the entanglements in space and motion of monomers along the primitive chain (reptation). Hence, in contrast to other long-time simulations based on the tube model, and similarly to conventional short-time molecular dynamics, the real space arrangement of the chains is accounted for. In this paper, extensions of the model towards fast flows, large deformations, branched polymers and polymer blends are introduced, in order to obtain simulations of polymeric systems with a variety of molecular structures over the longest relaxation time of the system. Quantitative tests against existing experimental data indicate good agreement with just two adjustable parameters, which are the scale factors in space and time.