In-plane and out-of-plane rotational motion of individual chain molecules in steady shear flow of polymer melts and solutions.

Recent nonequilibrium molecular dynamics (NEMD) simulations of mildly entangled CH and moderately entangled CH linear polyethylene melts undergoing steady shear flow have revealed that several inconsistencies between theory and experiment could be rectified by consideration of the rotational motion of individual polymer chains that occurs at moderate to high flow strengths. In this study, we investigated the configurational dynamics of the individual molecular chains that allow these once-entangled, long-chain molecules to execute retraction/extension semi-periodic cycles in response to the imposed shear via NEMD simulations. Brownian dynamics simulations were also performed to extract dynamical and configurational information about the similar cycles of polymer chain behavior that occur in dilute solutions of macromolecular chain liquids dissolved in low molecular weight solvents.