Molecular Dynamics Simulation of Stretch-Induced Crystallization in Polyethylene: Emergence of Fiber Structure and Molecular Network

Abstract

Molecular processes of fiber formation and network genesis in polyethylene (PE) are studied by molecular dynamics simulation of crystallization from highly stretched melt. We consider a system comprising 150 molecules of 500 united atoms, which is much larger than that of our previous work on fiber structures and their deformation [Polymer 2013, 54, 3086], aiming to study crystal nucleation and growth separately. Rapid elongation of the isotropic melt gives rise to incipient crystal clusters or embryos much smaller than critical nuclei. Subsequent isothermal crystallization of the stretched melt leads to three distinct stages of structure formation. The initial stage is a period waiting for critical nucleation. In the second stage that follows, we observe independent growth of isolated lamellae and resulting polynomial increases in crystallinity. In the last stage the crystals come to collide with each other to give well-aligned stacked lamellae. By dividing the system into mesh cells (pixels) and using a...