(338ah) Molecular Dynamic Simulations of Intercrystalline Phases during Polyethylene Crystallization

We apply atomistic molecular dynamics simulations to investigate the structural evolution in the intercrystalline phases of polyethylene (PE) during crystallization. Two crystalline seeds with various relative orientations and distances are placed in molten PE samples to trigger instantaneous crystallization under quiescent conditions. Using the Z1+ algorithm, we monitor the distributions of entanglement among the amorphous chains during crystallization. We show that crystal growth requires alignment and disentanglement of polymer strands. With increasing crystallinity, the polymer chains become immobilized near the crystals. A layer of “fixed” entanglement accumulates near the crystal surface, and in turn, hinders the crystal growth. We also investigate the stress transmitters, including tie chains and entangled loops, in the intercrystalline phase. The tie chain fraction increases with increasing molecular weight and decreasing inter-crystal distance. Our results fit well with the prediction of the modified Huang-Brown model when the inter-crystal distance is comparable to or larger than the root mean squared end-to-end distance of polymer chains.