Molecular dynamics simulation of polymer crystallization from the melt

This paper is an extension of our previous work (J. Chem. Phys. 115, 8675 (2001)) on the molecular dynamics simulation of polymer crystallization from the melt. In order to accelerate crystallization, a simplified molecular model of polymethylene is used as before; the polymer chain is made of 100 beads (CH2 united atoms) connected by harmonic springs; the lowest energy conformation consists of a fully stretched form with a slight bending stiffness. In order to reduce finite size effects on the simulation, the present work treats a much larger system, made of 640 chains of C-100. The molecules are placed between two parallel substrates that represent the growth surfaces of two lamellae growing toward each other. An initial melt state generated at 600 K is rapidly quenched to various crystallization temperatures, and the molecular processes of crystallization that follow are investigated. We again notice the growth of stacked lamellae from both substrates. The growing lamellae are found to have a marked tapered shape and to show thickening growth along the chain axis as well as normal growth. The growth rate of the lamellae is found to be sensitive to the temperature of crystallization. The molecular trajectories and the changes in the chain extension during crystallization are also investigated. In addition, we find no appreciable order within the undercooled melt phase under the melting point.