A reptation-based lattice model with tube-chain coupling for the linear dynamics of bidisperse entangled linear polymer

A reptation-based lattice model for simulating the linear dynamics of entangled linear polymers that accounts for an essential coupling in tube-chain motions during constraint release is proposed. The predictions are tested against a representative set of dynamic oscillatory data on bidisperse polybudadiene (PBd) melts. The special feature of the current model lies in that the motion of the primitive chain coincides exactly with that of the 'tube,' so that it is possible to mimic the longitudinal relaxation that is cooperative with the lateral one (i.e., double reptation) during constraint release. The simulation is shown to capture the central feature of constraint release for the investigated system without demanding factorizability for the stress relaxation function, as usually enforced in existing tube theories. Furthermore, the simulation suggests that the longitudinal chain relaxation currently incorporated might account for an important partition of stress relaxation that had customarily been attributed to the effect of double reptation or similar tube motions alone.