Gabana, K., Gehring, G.A., Meyer, H. et al. (3 more authors) (2024) Molecular simulations of quantized lamellar thickening in polyethylenes with regularly spaced brominated groups. Macromolecules, 57 (24). pp. 11311-11321. ISSN 0024-9297
Abstract
Polyethylene (PE) chains, with CH2 groups replaced by CBr2 at regular intervals (“precision PE”), have been observed to exhibit competing polymorphs driven by a preference for quantized fold lengths by Tasaki et al. [Macromolecules, 2014, 47, 4738-4749]. Motivated by this recent discovery, the crystallization behavior of such precision PE chains, 400 carbons long with CBr2 groups placed regularly at every 21st carbon, is investigated using molecular dynamics simulations. The united-monomer model of PE is extended to include dibromo groups, with steric clashes at the bromines reflected in a triple-well bending potential, demonstrating its function as a preferred fold site. Different crystallization protocols, continuous-cooling and self-seeding, reveal remarkably different crystals. Using self-seeding, the crystalline lamellar thickness increases monotonically with temperature, in quantized multiples of the distance between dibromo units. Polymer chains are observed to fold preferentially at the dibromo groups, and such groups appear to be tolerated within the crystal lamellae. On quenching the bromos assemble to form registered layers, not unlike Smectic phases observed in liquid crystals, which confirms the experimental observation of competing Form I and Form I′ polymorphs.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2024 The Authors. Except as otherwise noted, this author-accepted version of a journal article published in Macromolecules is made available via the University of Sheffield Research Publications and Copyright Policy under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ |
Keywords: | Bromine; Crystal structure; Crystallization; Crystals; Polyethylene |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > School of Chemical, Materials and Biological Engineering |
Funding Information: | Funder Grant number ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/T003294/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 21 Jan 2025 14:40 |
Last Modified: | 22 Jan 2025 14:30 |
Status: | Published |
Publisher: | American Chemical Society (ACS) |
Refereed: | Yes |
Identification Number: | 10.1021/acs.macromol.4c02209 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:222040 |