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Swelling of Cellulose Fibrillar Matrices and Gels
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]

One of the major challenges of today´s society is to find a sustainable way to create a living based on the resources on earth. It is a challenge that includes a transition from fossil-based materials to renewable/biodegradable raw materials and also the creation of an environmentally friendly circular material flow. In the search for renewable and biodegradable raw materials, the forest has gained renewed interest. In Sweden, 70 % of the area is covered with forest and, together with a long history of a sustainable forestry, this means that there are environmental and economic gains if this resource is utilized in a correct way and research and development into new wood-based materials has advanced significantly during the last decades. The wood component that has gained the most attention is cellulose and due to the ability of cellulose to act as a light-weight reinforcing component in composites and also due to the variability by which cellulose can be modified in order to obtain a wide range of useful properties. One advantage of cellulose-based materials is that they can be processed in water since the cellulose is hydrophilic and is softened by exposure to water. At the same time, this is one of the major drawbacks of cellulose-based materials since their properties deteriorate when exposed to water, whether as moist air or as condensed liquid. To optimize the use of cellulose fibers/fibrils/gels, knowledge of the effect on the inherent properties of cellulose in contact with water needs to be extended. This project has therefore focused on a fundamental understanding of the reasons behind the water uptake/swelling in a cellulose-rich fiber assembly immersed in water.

The project has included the development and characterization of cellulose model materials in the form of gel (beads) and fibrillar (filaments) networks, for which the swelling was measured as a dimensional change in different aqueous environments. In one of the subprojects, the ion-induced swelling in different cellulose networks was measured on model materials and it was shown that the ion-induced contribution to the swelling was not only dependent on pH and salt concentration in the aqueous solution but also on the stiffness and structure of the network. Thermodynamic models describing gel swelling were used to separate and quantify the osmotic pressure associated with different factors contributing to the total osmotic pressure (ions, mixing and network) of never-dried gel beads. It was thus possible to identify the factor which had a dominant influence in the osmotic pressure and hence most important on the swelling of the systems. Never-dried gel beads showed that the network entropy was the most important factor controlling the swelling of the beads up to a volume fraction of cellulose of 35 %. Above this volume fraction the mixing entropy was found to dominate the swelling. It was also found that the distribution of the total osmotic pressure on these three factors was dependent on the network structure, as the distribution changed when the beads were dried and rewetted compared to the never-dried beads. Finally the de-watering ability of the gel beads in different environments was studied, and also after different modifications targeting the properties shown to have the most dominant effect on the osmotic swelling pressure (ion, mix and network). It was possible to quantify how the gel beads were dewatered to different degrees if e.g. hydrogen was chosen as the counter-ion to the carboxyl groups, if the polarity of the solution was lowered and if the structure of cellulose was changed. This information can, for example, be used to predict how nanocellulose based networks are dewatered under different conditions and this is essential for the preparation of materials based on cellulose nanofibrils.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. , p. 68
Series
TRITA-CBH-FOU ; 2019:22
Keywords [en]
swelling, hydrogel, cellulose, wood, cellulose fibrils
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-250026ISBN: 978-91-7873-168-8 (print)OAI: oai:DiVA.org:kth-250026DiVA, id: diva2:1307044
Public defence
2019-05-24, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20190425

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-04-25Bibliographically approved
List of papers
1. Internal Structure of Isolated Cellulose I Fibril Aggregates in the Water Swollen State
Open this publication in new window or tab >>Internal Structure of Isolated Cellulose I Fibril Aggregates in the Water Swollen State
2017 (English)In: Nanocelluloses: Their Preparation, Properties and Applications, Washington, DC: American Chemical Society (ACS), 2017Chapter in book (Refereed)
Abstract [en]

By combining H-2-NMRD and CP/MAS C-13-NMR measurements of water-based cellulose gels and of water swollen pulps it was possible to estimate the nature of the interior structure of cellulose fibril aggregates. A set of samples with high cellulose purity and low charge was used. The interpretation of data was based on a relaxation model describing the exchange dynamics for deuterium exchange between water molecules and cellulose hydroxyl groups. The theoretical model used made it possible to calculate cellulose surface-to-volume ratios (q-values) from both H-2-NMRD and CP/MAS C-13-NMR data. Good consistency between H-2-NMRD and CP/MAS C-13-NMR data was found. In all investigated samples the cellulose fibril aggregates showed a different degree of "openness" interpreted as the presence of interstitial water inside fibril aggregates. One result also showed that an increased degree of fibril aggregate openness results from the TEMPO-oxidation. Common to all samples was that in the water swollen state water molecules could access part of the fibril aggregate interior.

Place, publisher, year, edition, pages
Washington, DC: American Chemical Society (ACS), 2017
Series
ACS Symposium Series
National Category
Polymer Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-250010 (URN)000417770800005 ()
Note

QC 20190520

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-05-20Bibliographically approved
2. Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers
Open this publication in new window or tab >>Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers
Show others...
2018 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 519, p. 119-129Article in journal (Refereed) Published
Abstract [en]

Macroscopic beads of water-based gels consisting of uncharged and partially charged beta-(1,4)-D-glucan polymers were developed to be used as a novel model material for studying the water induced swelling of the delignified plant fiber walls. The gel beads were prepared by drop-wise precipitation of solutions of dissolving grade fibers carboxymethylated to different degrees. The internal structure was analyzed using Solid State Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance and Small Angle X-ray Scattering showing that the internal structure could be considered a homogeneous, non-crystalline and molecularly dispersed polymer network. When beads with different charge densities were equilibrated with aqueous solutions of different ionic strengths and/or pH, the change in water uptake followed the trends expected for weak polyelectrolyte gels and the trends found for cellulose-rich fibers. When dried and subsequently immersed in water the beads also showed an irreversible loss of swelling depending on the charge and type of counter-ion which is commonly also found for cellulose-rich fibers. Taken all these results together it is clear that the model cellulose-based beads constitute an excellent tool for studying the fundamentals of swelling of cellulose rich plant fibers, aiding in the elucidation of the different molecular and supramolecular contributions to the swelling.

Place, publisher, year, edition, pages
Academic Press, 2018
Keywords
Swelling, Water uptake, Hydrogel, Cellulose, Small-angle X-ray scattering, Solid state NMR, Atomic force microscopy
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-226733 (URN)10.1016/j.jcis.2018.02.052 (DOI)000429633500013 ()29486431 (PubMedID)2-s2.0-85042413398 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20180503

Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2019-04-25Bibliographically approved
3. Measuring elasticity of wet cellulose beads with an AFM colloidal probe using a linearized DMT model
Open this publication in new window or tab >>Measuring elasticity of wet cellulose beads with an AFM colloidal probe using a linearized DMT model
2017 (English)In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 9, no 27, p. 4019-4022Article in journal (Refereed) Published
Abstract [en]

The mechanical properties of wet cellulose are investigated using an atomic force microscope AFM and calculated using a linearized DMT model. Measurements were performed using a model system of gel beads made of cellulose with different charge densities, which show a high impact on the mechanical properties of the cellulose in wet state.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-215478 (URN)10.1039/c7ay01219e (DOI)000411460700001 ()2-s2.0-85023750517 (Scopus ID)
Note

QC 20171013

Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2019-05-22Bibliographically approved
4. Elasticity and Ion-Induced Swelling of Cellulose Fibrillar Networks and Gels
Open this publication in new window or tab >>Elasticity and Ion-Induced Swelling of Cellulose Fibrillar Networks and Gels
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-250014 (URN)
Note

QC 20190521

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-05-21Bibliographically approved
5. Thermodynamics of the Water-Retaining Properties of Cellulose-Based Networks
Open this publication in new window or tab >>Thermodynamics of the Water-Retaining Properties of Cellulose-Based Networks
2019 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 20, no 4, p. 1603-1612Article in journal (Refereed) Published
Abstract [en]

Noncrystalline cellulose-based gel beads were used as a model material to investigate the effect of osmotic stress on a cellulosic network. The gel beads were exposed to osmotic stress by immersion in solutions with different concentrations of high molecular mass dextran and the equilibrium dimensional change of the gel beads was studied using optical microscopy. The volume fraction of cellulose was calculated from the volume of the gel beads in dextran solutions and their dry content and the relation between the cellulose volume fraction and the total osmotic pressure was thus obtained. The results show that the contribution to the osmotic pressure from counterions increases the water-retaining capacity of the beads at high osmotic pressures but also that the main factor controlling the gel bead collapse at high osmotic strains is the resistance to the deformation of the polymer chain network within the beads. Furthermore, the osmotic pressure associated with the deformation of the polymer network, which counteracts the deswelling of the beads, could be fitted to the Wall model indicating that the response of the cellulose polymer networks was independent of the charge of the cellulose. The best fit to the Wall model was obtained when the Flory-Huggins interaction parameter () of the cellulose-water system was set to 0.55-0.60, in agreement with the well-established insolubility of high molecular mass β-(1,4)-d-glucan polymers in water.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Polymer Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-250012 (URN)10.1021/acs.biomac.8b01791 (DOI)000464248300013 ()2-s2.0-85063128803 (Scopus ID)
Note

QC 20190509

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-05-22Bibliographically approved
6. De-watering of Cellulose-based Gel Networks Targeting Different Factors Contributing to the Swelling Pressure
Open this publication in new window or tab >>De-watering of Cellulose-based Gel Networks Targeting Different Factors Contributing to the Swelling Pressure
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-250025 (URN)
Note

QC 20190521

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-05-21Bibliographically approved

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The full text will be freely available from 2021-12-31 14:00
Available from 2021-12-31 14:00

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