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Tailoring Cellulose Nanofibrils for Advanced Materials
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.ORCID iD: 0000-0002-4100-6076
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cellulose nanofibrils (CNFs) are nanoscale fibers of high aspect ratio that can be isolated from a wide variety of cellulosic sources, including wood and bacterial cellulose. With high strength despite of their low density, CNFs are a promising renewable building block for the preparation of nanostructured materials and composites. To fabricate CNF-based materials with improved inherent rheological and mechanical properties and additional new functionalities, it is essential to tailor the surface properties of individual CNFs. The surface structures control the interactions between CNFs and ultimately dictate the structure and macroscale properties of the bulk material. In this thesis we have demonstrated different approaches, ranging from non-covalent adsorption and covalent chemical modification to modification of cellulose biosynthesis, to tailor the structure and surface functionalities of CNFs for the fabrication of advanced materials. These materials possess enhanced properties such as water-redispersibility, water absorbency, dye adsorption capacity, antibacterial activity, and mechanical properties.

In Paper I, CNFs were modified via the irreversible adsorption of carboxymethyl cellulose (CMC). The adsorption of small amounts of CMC onto the surface of CNFs prevented agglomeration and co-crystallization of the nanofibrils upon drying, and allowed the recovery of rheological and mechanical properties after redispersion of dried CNF samples.

In Paper II, CNFs bearing permanent cationic charges were prepared through quaternization of wood pulp fibers followed by mechanical disintegration. The activation of the hydroxyl groups on pulp fibers by alkaline treatment was optimized prior to quaternization. This optimization resulted in individual CNFs with uniform width and tunable cationic charge densities. These cationic CNFs demonstrated ultrahigh water absorbency and high adsorption capacity for anionic dyes.

In Paper III, via a similar approach as in Paper II, CNFs bearing polyethylene glycol (PEG) were prepared by covalently grafting PEG to carboxylated pulp fibers prior to mechanical disintegration. CNFs with a high surface chain density of PEG and a uniform width were oriented to produce macroscopic ribbons simply by mechanical stretching of the CNF hydrogel network before drying. The uniform grafted thin monolayer of PEG on the surface of individual CNFs prevented the agglomeration of CNFs and facilitated their alignment upon mechanical stretching, thus resulted in ribbons with ultrahigh tensile strength and modulus. These optically transparent ribbons also demonstrated interesting biaxial light scattering behavior.

In Paper IV, bacterial cellulose (BC) was modified by the addition of chitin nanocrystals (ChNCs) into the growing culture medium of the bacteria Acetobacter aceti which secretes cellulose in the form of entangled nanofibers. This led to the in situ incorporation of ChNCs into the BC nanofibers network and resulted in BC/ChNC nanocomposites exhibiting bactericidal activity. Further, blending of BC nanofibers with ChNCs produced nanocomposite films with relatively lower tensile strength and modulus compared to the in situ cultivated ones. The bactericidal activity increased significantly with increasing amount of ChNCs for nanocomposites prepared by direct mixing of BC nanofibers and ChNCs.

In Paper V, CNFs were isolated from suspension-cultured wild-type (WT) and cellulose-binding module (CBM) transformed tobacco BY-2 (Nicotiana tabacum L. cv bright yellow) cells. Results from strong sulfuric acid hydrolysis indicated that CNFs from transgenic cells overexpressing CBM consisted of longer cellulose nanocrystals compared to CNFs from WT cells. Nanopapers prepared from CNFs of transgenic cells demonstrated significantly enhanced toughness compared to CNFs of WT cells.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , 82 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:52
Keyword [en]
cellulose nanofibrils, bacterial cellulose, surface modification, carboxymethyl cellulose, polyethylene glycol, chitin nanocrystals, bactericidal activity, nanofibrils orientation, water redispersability, mechanical properties, dye removal
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-155056ISBN: 978-91-7595-329-8 (print)OAI: oai:DiVA.org:kth-155056DiVA: diva2:759415
Public defence
2014-11-21, sla F3, Lindstedtsvägen 26, KTH, Stockholm, 13:30 (English)
Opponent
Supervisors
Projects
CARBOMAT
Funder
Formas, CARBOMAT
Note

QC 20141103

Available from: 2014-11-03 Created: 2014-10-29 Last updated: 2014-11-14Bibliographically approved
List of papers
1. Water redispersible cellulose nanofibrils adsorbed with carboxymethyl cellulose
Open this publication in new window or tab >>Water redispersible cellulose nanofibrils adsorbed with carboxymethyl cellulose
2014 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 6, 4349-4358 p.Article in journal (Refereed) Published
Abstract [en]

Cellulose nanofibrils (CNFs) are difficult to redisperse in water after they have been completely dried due to the irreversible agglomeration of cellulose during drying. Here, we have developed a simple process to prepare water-redispersible dried CNFs by the adsorption of small amounts of carboxymethyl cellulose (CMC) and oven drying. The adsorption of CMC onto CNFs in water suspensions at 22 and 121 °C was studied, and the adsorbed amount of CMC was measured via conductimetric titration. The water-redispersibility of dried CNFs adsorbed with different amounts of CMC was characterized by sedimentation test. Above a critical threshold of CMC adsorption, i.e. 2.3 wt%, the oven dried CNF–CMC sample was fully redispersible in water. The morphology, rheological, and mechanical properties of water-redispersed CNF–CMC samples were investigated by field emission scanning electron microscopy, viscosity measurement, and tensile test, respectively. The water-redispersed CNFs preserved the original properties of never dried CNFs. This new method will facilitate the production, transportation and storage, and large-scale industrial applications of CNFs.

Keyword
Cellulose nanofibrils, Carboxymethyl cellulose, Adsorption, Redispersion
National Category
Organic Chemistry Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-155178 (URN)10.1007/s10570-014-0452-7 (DOI)000344802700041 ()2-s2.0-84911998076 (Scopus ID)
Funder
Formas, 2009-1687
Note

QC 20141103

Available from: 2014-11-03 Created: 2014-11-03 Last updated: 2017-12-05Bibliographically approved
2. Surface quaternized cellulose nanofibrils with high water absorbency and adsorption capacity for anionic dyes
Open this publication in new window or tab >>Surface quaternized cellulose nanofibrils with high water absorbency and adsorption capacity for anionic dyes
2013 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, no 6, 2047-2055 p.Article in journal (Refereed) Published
Abstract [en]

Surface quaternized cellulose nanofibrils were mechanically disintegrated from wood pulp that was pretreated through a reaction with glycidyltrimethylammonium chloride. The resulting quaternized cellulose nanofibrils (Q-NFC) with trimethylammonium chloride contents of 0.59-2.31 mmol g(-1) were characterized by conductometric titration, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). When the trimethylammonium chloride content on cellulose reached approximately 0.79 mmol g(-1) corresponding to a degree of substitution of 0.13 per bulk anhydroglucose unit, highly viscous and transparent aqueous dispersions of cellulose nanofibrils were obtained by mechanical homogenization of the chemically pretreated cellulose/water slurries. AFM observation showed that the dispersions consisted of individualized cellulose I nanofibrils 1.6-2.1 nm in width and 1.3-2.0 mu m in length. Cellulose nanopapers prepared from the Q-NFC aqueous dispersions exhibited high tensile strength (ca. 200 MPa) and Young's modulus (ca. 10 GPa) despite high porosity (37-48%). The nanopapers also demonstrated ultrahigh water absorbency (750 g g(-1)) with high surface cationic charge density. Stable hydrogels were obtained after swelling the nanopaper in water. The Q-NFC nanofibrils also possessed high anionic dye adsorption capability. The adsorption capacity increased with increasing trimethylammonium chloride content on cellulose.

Keyword
Tempo-Mediated Oxidation, Ion-Exchange Celluloses, Polyacrylic-Acid Chains, Free-Floating Cotton, Waste-Water, Microfibrillated Cellulose, Ammonium Functions, Textile-Industry, Native Cellulose, Polymer Nanocomposites
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-118256 (URN)10.1039/c2sm27344f (DOI)000313594200037 ()2-s2.0-84872519329 (Scopus ID)
Note

QC 20130214

Available from: 2013-02-14 Created: 2013-02-14 Last updated: 2017-12-06Bibliographically approved
3. Transparent, hazy and strong macroscopic ribbon of oriented cellulose nanofibrils bearing poly(ethylene glycol)
Open this publication in new window or tab >>Transparent, hazy and strong macroscopic ribbon of oriented cellulose nanofibrils bearing poly(ethylene glycol)
(English)Manuscript (preprint) (Other academic)
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-155181 (URN)
Note

QS 2014

Available from: 2014-11-03 Created: 2014-11-03 Last updated: 2014-11-03Bibliographically approved
4. Nanocomposites of bacterial cellulose nanofibers and chitin nanocrystals: fabrication, characterization and bactericidal activity
Open this publication in new window or tab >>Nanocomposites of bacterial cellulose nanofibers and chitin nanocrystals: fabrication, characterization and bactericidal activity
Show others...
2013 (English)In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 15, no 12, 3404-3413 p.Article in journal (Refereed) Published
Abstract [en]

An environmentally friendly approach was implemented for the production of nanocomposites with bactericidal activity, using bacterial cellulose (BC) nanofibers and chitin nanocrystals (ChNCs). The antibacterial activity of ChNCs prepared by acid hydrolysis, TEMPO-mediated oxidation or partial deacetylation of a-chitin powder was assessed and the structure of the ChNC nanoparticles was characterized by X-ray diffraction, atomic force microscopy, and solid-state C-13-NMR. The partially deacetylated ChNCs (D-ChNC) showed the strongest antibacterial activity, with 99 +/- 1% inhibition of bacterial growth compared to control samples. Nanocomposites were prepared from BC nanofibers and D-ChNC by (i) in situ biosynthesis with the addition of D-ChNC nanoparticles in the culture medium of Acetobacter aceti, and (ii) post-modification by mixing D-ChNC with disintegrated BC in an aqueous suspension. The structure and mechanical properties of the BC/D-ChNC nanocomposites were characterized by Fourier transform infrared spectroscopy, elemental analysis, field-emission scanning electron microscopy, and an Instron universal testing machine. The bactericidal activity of the nanocomposites increased with the D-ChNC content, with a reduction in bacterial growth by 3.0 log units when the D-ChNC content was 50%. D-ChNC nanoparticles have great potential as substitutes for unfriendly antimicrobial compounds such as heavy metal nanoparticles and synthetic polymers to introduce antibacterial properties to cellulosic materials.

Keyword
Alpha-Chitin, Antibacterial Activity, Biomedical Applications, Mechanical-Properties, Nanopaper Structures, Molecular-Weight, In-Vitro, Chitosan, Composite, Films
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-138389 (URN)10.1039/c3gc41700j (DOI)000327459400015 ()2-s2.0-84888273107 (Scopus ID)
Funder
Formas, 2009-1687
Note

QC 20131220

Available from: 2013-12-20 Created: 2013-12-19 Last updated: 2017-12-06Bibliographically approved
5. Enhancing toughness of cellulose nanofibrils through the expression of cellulose-binding modules in plant
Open this publication in new window or tab >>Enhancing toughness of cellulose nanofibrils through the expression of cellulose-binding modules in plant
(English)Manuscript (preprint) (Other academic)
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-155180 (URN)
Note

QS 2014

Available from: 2014-11-03 Created: 2014-11-03 Last updated: 2014-11-14Bibliographically approved

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