A MOLECULAR-DYNAMICS STUDY OF POLYETHYLENE CRYSTALLIZATION

Molecular dynamics simulations of model polyethylene chains of various lengths were performed. The occurrence of a few gauche states promotes long range attractive interactions between segments and causes the chain to fold into lamellae, via a global collapse mechanism. In the absence of the torsion potential, a two stage collapse process was seen, in which the chain forms local collapsed domains, which then coalesce into a large lamella. Simulations corresponding to elevated temperatures showed similar features. The calculated radii of gyration R(g) of chains of various lengths show the same trend as the experimental results on solution crystallized polyethylene. The predominance of the trans conformation in the collapsed state indicates that substantial local order might be present in the melt.