Molecular dynamics studies of the effects of branching characteristics on the crystalline structure of polyethylene

Doran, Michael & Choi, Phillip (2001) Molecular dynamics studies of the effects of branching characteristics on the crystalline structure of polyethylene. The Journal of Chemical Physics, 115(6), pp. 2827-2830.

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Abstract

Molecular dynamics simulations were carried out on single chain models of linear low-density polyethylene in vacuum to study the effects of branch length, branch content, and branch distribution on the polymer’s crystalline structure at 300 K. The trans/gauche (t/g) ratios of the backbones of the modeled molecules were calculated and utilized to characterize their degree of crystallinity. The results show that the t/g ratio decreases with increasing branch content regardless of branch length and branch distribution, indicating that branch content is the key molecular parameter that controls the degree of crystallinity. Although t/g ratios of the models with the same branch content vary, they are of secondary importance. However, our data suggests that branch distribution (regular or random) has a significant effect on the degree of crystallinity for models containing 10 hexyl branches/1,000 backbone carbons. The fractions of branches that resided in the equilibrium crystalline structures of the models were also calculated. On average, 9.8% and 2.5% of the branches were found in the crystallites of the molecules with ethyl and hexyl branches while C13 NMR experiments showed that the respective probabilities of branch inclusion for ethyl and hexyl branches are 10% and 6% [Hosoda et al., Polymer 1990, 31, 1999–2005]. However, the degree of branch inclusion seems to be insensitive to the branch content and branch distribution.

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ID Code: 55606
Item Type: Journal Article
Refereed: Yes
Keywords: polyethylene, crystallisation, thermodynamics
DOI: 10.1063/1.1386907
ISSN: 1089-7690
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > MACROMOLECULAR AND MATERIALS CHEMISTRY (030300)
Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > THEORETICAL AND COMPUTATIONAL CHEMISTRY (030700) > Statistical Mechanics in Chemistry (030704)
Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > MATERIALS ENGINEERING (091200) > Polymers and Plastics (091209)
Divisions: Current > Schools > School of Biomedical Sciences
Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2001 American Institute of Physics
Copyright Statement: This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Deposited On: 14 Dec 2012 00:22
Last Modified: 14 Dec 2012 22:14

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