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On the Solubility of Wood Hemicelluloses in Water and its Influence on the Adsorption at Cellulose/Water Interfaces
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hemicelluloses are a group of natural polysaccharides and one of the main components of wood. The availability and biodegradability of these polymers have created a great interest in developing new bio-based materials or composites from these materials for different end-use purposes. To develop new materials from these polysaccharides with better functionalities, it is essential to understand the fundamental properties of these compounds. The solubility of hemicelluloses is one of these crucial characteristics since the material has to be dissolved in an appropriate solvent if these biopolymers are to be used in, for example, dense and strong films once the solvents are removed. The interaction of these polysaccharides with different solid surfaces is also significantly influenced by their solubility at the surface/water interface and an understanding of this interaction is essential for describing composite formation, since the polysaccharides are most frequently used together with reinforcing materials such as anisotropic cellulose fibers and fibrils.

In the work described in this thesis, a novel methodology has been developed for characterizing in detail the solubility of the extracted and model mannans, arabinoxylans and xyloglucan polysaccharides. Different chemical structural analyses, chromatography, light scattering and microscopy techniques have been applied to achieve an accurate understanding of the solubility of the polysaccharides in aqueous media. A careful study has been performed to isolate and purify softwood polysaccharides, followed by the preparation of model samples to investigate the influence of processing, structural substitutions and molar mass on the solubility. Association and the phase separation of hemicelluloses have been identified in aqueous media despite their clear and transparent appearance to the naked eye.

Natural hemicelluloses are used in combination with cellulose as composite materials both to introduce different functionalities and to utilize the great mechanical properties of cellulose fibrils/fibers. Accordingly, there was a great need to study the influence of the solubility on the interaction and adsorption of these polysaccharides at the cellulose/water interface. The adsorption at the cellulose/water interface was indeed affected by the physicochemical structures and solubility of the polysaccharides, and it has been shown that an increasing molar mass and an increasing polymer concentration lead to formation of associated structures and a phase separation at cellulose model surfaces.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. , p. 60
Series
TRITA-CBH-FOU ; 2019:29
Keywords [en]
Wood, Hemicellulose, Solubility, Adsorption, Interaction, Cellulose, Size distribution
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-251110ISBN: 978-91-7873-190-9 (electronic)OAI: oai:DiVA.org:kth-251110DiVA, id: diva2:1314627
Public defence
2019-06-07, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2019-05-09

Available from: 2019-05-09 Created: 2019-05-09 Last updated: 2019-05-13Bibliographically approved
List of papers
1. Solubility of Softwood Hemicelluloses
Open this publication in new window or tab >>Solubility of Softwood Hemicelluloses
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2018 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 4, p. 1245-1255Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that the molecular solubility of softwood hemicelluloses is significantly influenced by pretreatment of the fibers, extraction, and downstream processing. To quantify these effects, four hemicellulose samples were extracted from different thermomechanical pulps of Norway spruce. The molecular solubility of the samples was characterized by size and molar mass distributions, and the morphology of the molecules was studied using high resolution microscopy techniques. All extracted samples were well dispersed in aqueous media creating transparent dispersions, but dynamic light scattering measurements showed that molecular solubility can only be achieved using specific pretreatments and extractions. The procedure yields acetylated galactoglucomannan (AcGGM)-rich hemicelluloses with an average molar mass of 21-35 kDa and a diameter up to 10 nm but also shows that water is a poor solvent for this sample since an association is detected as soon as the concentration is about 20 g/L. These associated hemicellulose dispersions are still absolutely dear on visual inspection, underlining the need for careful measurement when assessing the solubility of wood hemicelluloses.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-226772 (URN)10.1021/acs.biomac.8b00088 (DOI)000429886500015 ()29522320 (PubMedID)2-s2.0-85045144605 (Scopus ID)
Note

QC 20180503

Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2019-05-09Bibliographically approved
2. Experimental and Theoretical Evaluation of the Solubility/Insolubility Spruce Xylan (Arabino Glucuronoxylan)
Open this publication in new window or tab >>Experimental and Theoretical Evaluation of the Solubility/Insolubility Spruce Xylan (Arabino Glucuronoxylan)
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2019 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 20, no 3, p. 1263-1270Article in journal (Refereed) Published
Abstract [en]

The molecular solubility of softwood arabinoglucuronoxylan (AGX) has been thoroughly investigated, and it has been shown that the chemical and physical structures of the extracted hemicellulose are not significantly influenced by different purification steps, but a transient molecular solubility of AGX was observed in aqueous media at low concentrations (1 g/L) when the dissolved macromolecules had a hydrodynamic diameter of up to 10 nm. A phase separation was detected when the concentration was increased to 15 g/L leading to an association of the smaller molecules into fractal structures with a considerably larger diameter, even though the dispersions were still transparent to ocular inspection. Dynamic Light Scattering and Cryo-Transmission Electron Microscopy showed dimensions in the range of 1000 nm. The phase separation of the sample was further characterized by estimating the χ-interaction parameter of AGX in water using the Flory-Huggins theory, and the results supported that water is a poor solvent for AGX. This behavior is crucial when films and hydrogels based on these biopolymers are made, since the association will dramatically affect barrier and mechanical properties of films made from these materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-248093 (URN)10.1021/acs.biomac.8b01686 (DOI)000461270500013 ()30689362 (PubMedID)2-s2.0-85061537168 (Scopus ID)
Note

QC 20190429

Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-05-22Bibliographically approved
3. The influence of solubility on the adsorption of different Xyloglucan fractions at Cellulose Water Interfaces
Open this publication in new window or tab >>The influence of solubility on the adsorption of different Xyloglucan fractions at Cellulose Water Interfaces
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Xylogucan (XG) fractions with different molar masses were prepared while preserving the natural structure of the XG. The solubility of the fractions was investigated using light- scattering, chromatography and microscopy techniques. The conformational changes of the XG molecules and their association and phase separation were investigated together with concentration and molar mass changes. The knowledge gained was then applied to investigate the interaction of different XG fractions at cellulose model surfaces using a quartz crystal microbalance with dissipation. The results indicate that there is a cluster formation and phase separation of the XG molecules at the cellulose/water interface induced by the increase in XG concentration close to the surface. Concomitantly, the adsorption regimes are altered for the XG fractions depending on the solubility properties, indicating that the insolubility, association and phase separation of XGs in aqueous media affect their interaction with cellulose. The study is of vital importance for improving the functionality of sustainable materials made from xyloglucan/cellulose natural composites.

National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-251109 (URN)
Note

QC 20190509

Available from: 2019-05-09 Created: 2019-05-09 Last updated: 2019-05-09Bibliographically approved
4. The influence of acetylation and sugar composition on the (in)solubility of mannans, their interaction with cellulose surfaces and thermal properties.
Open this publication in new window or tab >>The influence of acetylation and sugar composition on the (in)solubility of mannans, their interaction with cellulose surfaces and thermal properties.
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(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-240496 (URN)
Note

QC 20190108

Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2019-05-09Bibliographically approved
5. Tailormade Polysaccharides with Defined Branching Patterns: Enzymatic Polymerization of Arabinoxylan Oligosaccharides
Open this publication in new window or tab >>Tailormade Polysaccharides with Defined Branching Patterns: Enzymatic Polymerization of Arabinoxylan Oligosaccharides
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2018 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, no 37, p. 11987-11992Article in journal (Refereed) Published
Abstract [en]

The heterogeneous nature of non-cellulosic polysaccharides, such as arabinoxylan, makes it difficult to correlate molecular structure with macroscopic properties. To study the impact of specific structural features of the polysaccharides on crystallinity or affinity to other cell wall components, collections of polysaccharides with defined repeating units are required. Herein, a chemoenzymatic approach to artificial arabinoxylan polysaccharides with systematically altered branching patterns is described. The polysaccharides were obtained by glycosynthase-catalyzed polymerization of glycosyl fluorides derived from arabinoxylan oligosaccharides. X-ray diffraction and adsorption experiments on cellulosic surfaces revealed that the physicochemical properties of the synthetic polysaccharides strongly depend on the specific nature of their substitution patterns. The artificial polysaccharides allow structure-property relationship studies that are not accessible by other means.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2018
Keywords
carbohydrates, enzymes, glycosynthases, structure elucidation, synthetic methods
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-235104 (URN)10.1002/anie.201806871 (DOI)000443675700024 ()30044516 (PubMedID)2-s2.0-85052657815 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20180917

Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2019-05-09Bibliographically approved

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Available from 2020-05-09 11:51

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