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Enhancing toughness of cellulose nanofibrils through the expression of cellulose-binding modules in plant
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.ORCID-id: 0000-0002-4100-6076
KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.ORCID-id: 0000-0001-9832-027X
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-155180OAI: oai:DiVA.org:kth-155180DiVA, id: diva2:760043
Merknad

QS 2014

Tilgjengelig fra: 2014-11-03 Laget: 2014-11-03 Sist oppdatert: 2014-11-14bibliografisk kontrollert
Inngår i avhandling
1. Tailoring Cellulose Nanofibrils for Advanced Materials
Åpne denne publikasjonen i ny fane eller vindu >>Tailoring Cellulose Nanofibrils for Advanced Materials
2014 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2014. s. 82
Serie
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:52
Emneord
cellulose nanofibrils, bacterial cellulose, surface modification, carboxymethyl cellulose, polyethylene glycol, chitin nanocrystals, bactericidal activity, nanofibrils orientation, water redispersability, mechanical properties, dye removal
HSV kategori
Forskningsprogram
Fiber- och polymervetenskap
Identifikatorer
urn:nbn:se:kth:diva-155056 (URN)978-91-7595-329-8 (ISBN)
Disputas
2014-11-21, sla F3, Lindstedtsvägen 26, KTH, Stockholm, 13:30 (engelsk)
Opponent
Veileder
Prosjekter
CARBOMAT
Forskningsfinansiär
Formas, CARBOMAT
Merknad

QC 20141103

Tilgjengelig fra: 2014-11-03 Laget: 2014-10-29 Sist oppdatert: 2014-11-14bibliografisk kontrollert

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