Molecular dynamics simulations of stretch-induced crystallization of polyethylene-grafted-graphene/polyethylene system

Abstract

The stretch-induced crystallization of the polyethylene (PE)-g-graphene/PE system was studied by molecular dynamics simulations. It was found that the stretching effect and the presence of grafted chains can enhance the orientation of segments along the stretching direction and promote the conformational transition of chains, leading to an increase in the content of precursors, thereby improving the crystallization ability of the polymer system. Detailed analysis revealed that the segments near grafting points, due to the strong restriction effect, have a significantly lower degree of orientational order and conformational transformation ability compared to the segments in the middle of the chains. For the segments near the free ends, due to the presence of more entanglements, the degree of orientational order and conformational transition ability are also significantly lower than those of the segments in the middle of the chains. Then, there is a higher precursor content for the segments in the middle of the chains compared to the segments near the ends, resulting in stronger crystallization ability of the segments in the middle of the chains. Additionally, it was found that the segments in the middle of the chains are more likely to form crystal nuclei through the intramolecular nucleation mechanism, while the segments near the ends tend to form crystal nuclei through the intermolecular nucleation mechanism.