The reorganization of the lamellar structure of a single polyethylene chain during heating: Molecular dynamics simulation

Molecular dynamics simulation starting from a lamellar crystal model of a s ingle polyethylene chain is performed to investigate the lamellar reorganiz ation during heating at the molecular level. It is shown that three stages are involved in the process of the reorganization: at temperatures 300 K<T< less than or equal to>370 K the lamella thickens, in the region of 370 K<T< less than or equal to>500 K the boundary premelting of the lamella occurs, and when T>500 K the lamella starts to melt and becomes a random coil in th e end. Particularly, the thickening process is investigated in our simulati ons. It is found that the lamellar thickening occurs in discrete steps and is driven mainly by the van der Waal attraction between the chain segments. There are two mechanisms for the lamellar thickening. At lower temperature the thickening occurs by the sliding diffusion of adjacent chain segments, while at higher temperature the recrystallization after the partial meltin g of thinner stems leads to the thickening. (C) 2001 American Institute of Physics.