Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: Polymer Crystallization and Semicrystalline Polymers

CPP 40.2: Vortrag

Donnerstag, 17. März 2011, 11:00–11:15, ZEU 160

Growth Pathway and Precursor States in Single Lamellar Crystallization: MD Simulations — •Chuanfu Luo and Jens-Uwe Sommer — Leibniz Institute of Polymer Research Dresden, Dresden, Germany

Molecular dynamics (MD) simulations are carried out to study the growth pathway of a single polymer crystal from a highly entangled dense melt via self-seeding[1]. Linear lateral growth, lamellar thickening and slipping of monomers along the chain direction are directly observed. We have introduced a measure of orientational-temporal persistence to characterize the state of monomer sequences out of equilibrium. This analysis allows us to define a birth-time for each stem and accordingly, folding kinetics of individual chains is analyzed as a function of their lifetime. Two stages can be identified for the growth of stem length with lifetime: The stem length increases linearly with lifetime at the precursor stage while it increases logarithmically at the thickening stage. Folds are created at the precursor stage and refolding events are statistically irrelevant. Precursor states can be identified as an early stage of a stem formed by semi-flexible segments. The semi-flexible segments are possessing orientational-temporal persistence which can potentially crystallize, and can be thus considered as unstable short stems. The classical Lauritzen-Hoffman (LH) or Sadler-Gilmer (SG) models are not consistent with our results which correspond to a time scale of about ≲45 ns. We thank DFG(SO 277/6-1) for financial support and ZIH of TU-Dresden for computing time. [1]C. Luo and J.-U. Sommer, Phys. Rev. Lett. 102, 147801 (2009)