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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Crystallization, Nucleation and Self-Assembly

CPP 19.2: Vortrag

Dienstag, 28. März 2023, 10:00–10:15, MER 02

Polyethylene crystallization induced by a solution-prefolded nucleus — •Timur Shakirov and Wolfgang Paul — University of Halle, Halle, Germany

We present results of molecular dynamics simulations of an undercooled polyethylene melt. We simulate a system of 2000 chains of 150 monomers each with the PYS force-field [1]. To initiate crystallization we insert in the melt a small two-chain nucleus (which we pre-fold in the vacuum) and cool down the system to 280 K. The crystalline lamella forms around the inserted nucleus during the cooling process and grows further at constant temperature. We characterize the growing crystallite by its average diameter (typical linear size in the cross-section perpendicular to the crystal director) and the height of the lamella (the averaged size along the crystal director). Both, diameter and height of lamella, grow during the entire simulation (~ 900 ns at the final temperature). A saturation of the growth is observed only as the crystallite reaches the surrounding spontaneously formed crystallites. Our analysis of the chain kinetics in the inner volume of the crystallite shows remaining chain mobility along the chain director. The distribution of short-time displacements of the inner-crystalline monomers has signatures of discrete jumps of a single bond length along the director of the crystal.

[1] W. Paul, D. Y. Yoon, and G. D. Smith, J. Chem. Phys. 103 (1995) 1702-1709.