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Deformation of cellulose allomorphs studied by molecular dynamics
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. Wallenberg Wood Science Center.ORCID iD: 0000-0002-0889-5940
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Cellulose-based materials draw their good mechanical properties from the cellu-lose crystal. Improved understanding of crystal properties could lead to a wider range of applications for cellulose-based materials, Cellulose crystals show high axial Youngs modulus. Cellulose can attain several allomorphic forms which show unique structural arrangements in terms of both intra-molecular and inter-molecular bonding, as well as unit cell parameters and chain packing. Although several studies have confirmed that mechanical tensile properties of cellulose differ between different allomorphic forms, few reports have investigated the deformation mechanisms explaining the differences.In the first part of this thesis, the tensile elastic Youngs modulus of cellulose allo-morphs Iβ, II and III I were calculated under uniform conditions using Molecular Dynamics simulation techniques. As expected, a difference in modulus valuesc ould be observed, and the cooperative nature of energy contributions to crys-tal modulus is apparent. The allomorphs also show large differences in terms of how contributions to elastic energy are distributed between covalent bonds,angles, dihedrals, electrostatic forces, dispersion and steric forces.In the second part of this thesis, the cellulose Iβ and II allomorphs were sub-jected to a more detailed structural study. The purpose was to clarify how the deformation of the central glucosidic linkage between the monomer units depends on the hydrogen-bonding structures. This was carried out by studying simulated vibrational spectra and local deformations in the crystals.The results presented in this thesis confirm the differences in the tensile elastic properties of these cellulose allomorphs. These differences can in part be explained by the different intra-molecular hydrogen bonding patterns between allomorphs. Deformation mechanisms are discussed. The results are in supportof the so called ”leverage effect” proposed in the literature. The present analysis shows significant differences in details of deformation mechanisms compared with previous simpler analyses.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2015. , 29 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:20
Keyword [en]
Cellulose, Polymer, Molecular Dynamics
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-166654ISBN: 978-91-7595-541-4 (print)OAI: oai:DiVA.org:kth-166654DiVA: diva2:811757
Presentation
2015-05-28, D3, Lindstedtsvägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 63625
Note

QC 20150518

Available from: 2015-05-18 Created: 2015-05-13 Last updated: 2015-05-18Bibliographically approved
List of papers
1. Molecular deformation mechanisms in cellulose allomorphs and the role of hydrogen bonds
Open this publication in new window or tab >>Molecular deformation mechanisms in cellulose allomorphs and the role of hydrogen bonds
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-166781 (URN)
Note

QS 2015

Available from: 2015-05-18 Created: 2015-05-18 Last updated: 2015-05-18Bibliographically approved
2. Molecular scale deformation mechanisms in cellulose crystals (I and II) by molecular dynamics - synergy between covalent and hydrogen bonds
Open this publication in new window or tab >>Molecular scale deformation mechanisms in cellulose crystals (I and II) by molecular dynamics - synergy between covalent and hydrogen bonds
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-166782 (URN)
Note

QS 2015

Available from: 2015-05-18 Created: 2015-05-18 Last updated: 2015-05-18Bibliographically approved

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Licentiate Thesis(5605 kB)243 downloads
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