View in EDS

Molecular Dynamics Simulation of Homogeneous CrystalNucleation in Polyethylene.

Saved in:
Bibliographic Details
Title: Molecular Dynamics Simulation of Homogeneous CrystalNucleation in Polyethylene.
Authors: Yi, Peng1, Locker, C. Rebecca1, Rutledge, Gregory C.1
Source: Macromolecules. Jun2013, Vol. 46 Issue 11, p4723-4733. 11p.
Subjects: Nucleation, Polyethylene, Molecular dynamics, Crystalline polymers, Temperature effect, Supercooling
Abstract: Using a realistic united-atom forcefield, molecular dynamics simulations were performed to study homogeneousnucleation of the crystal phase at about 30% supercooling from themelts of n-pentacontahectane (C150) and a linearpolyethylene (C1000), both of which are long enough to exhibit thechain folding that is characteristic of polymer crystallization. Thenucleation rate was calculated and the critical nuclei were identifiedusing a mean first-passage time analysis. The nucleation rate wasfound to be insensitive to the chain length in this range of molecularweight. The critical nucleus contains about 150 carbons on averageand is significantly smaller than the radius of gyration of the chains,at this supercooling. A cylinder model was used to characterize theshape of the crystal nuclei and to calculate the interfacial freeenergies. A chain segment analysis was performed to characterize thetopology of the crystal surface in terms of loops (including folds)and tails. The length distribution of loops is broad, supporting the“switchboardmodel” for the early stage crystals formed at deep supercooling.Using the survival probability method, the critical nucleus size wasdetermined as a function of temperature. The interfacial free energieswere found to be temperature-dependent. The free energy barrier andnucleation rate as functions of temperature were also calculated andcompare favorably with experiments. [ABSTRACT FROM AUTHOR]
Copyright of Macromolecules is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
Description
Abstract:Using a realistic united-atom forcefield, molecular dynamics simulations were performed to study homogeneousnucleation of the crystal phase at about 30% supercooling from themelts of n-pentacontahectane (C150) and a linearpolyethylene (C1000), both of which are long enough to exhibit thechain folding that is characteristic of polymer crystallization. Thenucleation rate was calculated and the critical nuclei were identifiedusing a mean first-passage time analysis. The nucleation rate wasfound to be insensitive to the chain length in this range of molecularweight. The critical nucleus contains about 150 carbons on averageand is significantly smaller than the radius of gyration of the chains,at this supercooling. A cylinder model was used to characterize theshape of the crystal nuclei and to calculate the interfacial freeenergies. A chain segment analysis was performed to characterize thetopology of the crystal surface in terms of loops (including folds)and tails. The length distribution of loops is broad, supporting the“switchboardmodel” for the early stage crystals formed at deep supercooling.Using the survival probability method, the critical nucleus size wasdetermined as a function of temperature. The interfacial free energieswere found to be temperature-dependent. The free energy barrier andnucleation rate as functions of temperature were also calculated andcompare favorably with experiments. [ABSTRACT FROM AUTHOR]
ISSN:00249297
DOI:10.1021/ma4004659