Assessment of entanglement features and dynamics from atomistic simulations and experiments in linear and short chain branched polyolefins

Abstract

We report on full atomistic computer simulations of the molecular dimensions and dynamics of molten entangled linear and short chain branched polyethylene chains of the same length with butyl branches content up to 55 per 1000 carbon atoms. This has been achieved by using a number of molecules equilibrated in all length scales by advanced Monte Carlo moves and Molecular Dynamics simulations. The simulations have been compared with published experimental results. With the increase in branching the simulations show: a chain contraction and higher flexibility of polymer chains; a higher effective step length of the primitive path and a slowing down of the chain dynamics. Furthermore the time evolution of the mean-square inner segments displacement is in quantitative agreement with the results obtained by incoherent neutron spin echo experiments for a monodisperse polyethylene sample with a similar molecular architecture. Finally, an anomalous subdiffusive behaviour of the centre of mass displacement is also predicted by the simulation, in accordance with recent theoretical approaches.