  The coupled dynamics of entangled polymers which span a broad time and length
scales govern the unique viscoelastic properties of polymers. To follow chain
mobility by numerical simulations from the intermediate Rouse and reptation
regimes to the late time diffusive regime, highly coarse grained models with
purely repulsive interactions between monomers are widely used since they are
computationally the most efficient. Here using large scale molecular dynamics
simulations the effect of including the attractive interaction between monomers
on the dynamics of entangled polymers melts is explored for the first time over
wide temperature range. Attractive interactions has little effect on the local
packing for all temperatures T and on the chain mobility for T higher than
about twice the glass transition Tg. These results, across a broad range of
molecular weight, show that to study the dynamics of entangled polymers melts
the interactions can be treated as pure repulsive, confirming a posteriori the
validity of previous studies and opening the way to new large scale numerical
simulations.
