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Cross-Linked and Shapeable Porous 3D Substrates from Freeze-Linked Cellulose Nanofibrils
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.ORCID iD: 0000-0003-1874-2187
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
RISE Bioecon, Papermaking & Packaging, Box 5604, SE-11486 Stockholm, Sweden..
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2019 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 20, no 2, p. 728-737Article in journal (Refereed) Published
Abstract [en]

Chemically cross-linked highly porous nano cellulose aerogels with complex shapes have been prepared using a freeze-linking procedure that avoids common post activation of cross-linking reactions and freeze-drying. The aerogel shapes ranged from simple geometrical three-dimensional bodies to swirls and solenoids. This was achieved by molding or extruding a periodate oxidized cellulose nanofibril (CNF) dispersion prior to chemical cross-linking in a regular freezer or by reshaping an already prepared aerogel by plasticizing the structure in water followed by reshaping and locking the aerogel into its new shape. The new shapes were most likely retained by new cross-links formed between CNFs brought into contact by the deformation during reshaping. This self-healing ability to form new bonds after plasticization and redrying also contributed to the mechanical resilience of the aerogels, allowing them to be cyclically deformed in the dry state, reswollen with water, and redried with good retention of mechanical integrity. Furthermore, by exploiting the shapeability and available inner structure of the aerogels, a solenoid-shaped aerogel with all surfaces coated with a thin film of conducting polypyrrole was able to produce a magnetic field inside the solenoid, demonstrating electromagnetic properties. Furthermore, by biomimicking the porous interior and stiff exterior of the beak of a toucan bird, a functionalized aerogel was created by applying a 300 mu m thick stiff wax coating on its molded external surfaces. This composite material displayed a 10-times higher elastic modulus compared to that of the plain aerogel without drastically increasing the density. These examples show that it is possible to combine advanced shaping with functionalization of both the inner structure and the surface of the aerogels, radically extending the possible use of CNF aerogels.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019. Vol. 20, no 2, p. 728-737
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-245946DOI: 10.1021/acs.biomac.8b01412ISI: 000458937200016PubMedID: 30394086Scopus ID: 2-s2.0-85057560598OAI: oai:DiVA.org:kth-245946DiVA, id: diva2:1295723
Conference
Symposium on Rational Design of Multifunctional Renewable-Resourced Materials held during the ACS National Meeting, AUG 19-23, 2018, Boston, MA
Note

QC 20190312

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-09-13Bibliographically approved
In thesis
1. CONTROLLED ASSEMBLY AND FUNCTIONALISATION OF CELLULOSE-BASED MATERIALS
Open this publication in new window or tab >>CONTROLLED ASSEMBLY AND FUNCTIONALISATION OF CELLULOSE-BASED MATERIALS
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The environmental effects caused by the use of fossil-based resources have intensified and driven society and research towards new materials and processes that utilise renewable resources. Within the development of new materials, wood has been identified as a raw-material from which high performing materials can be derived. One such material is cellulose nanofibrils (CNFs) which are capable of replacing several currently used fossil-based materials. However, for CNFs to exhibit the required material properties they need to be chemically or physically modified. This means that the properties of the CNFs can be specifically adapted to fit the demand in particular areas, for example electrical energy storage. In these applications it is the mechanical properties; the large, easily functionalised surface and ability to be moulded into 3D shapes that make CNFs a highly interesting raw material.

This thesis explores the formation and functionalisation of CNF- and fibre-based materials and their novel use in applications such as energy storage. The wet stability of the materials was achieved by crosslinking and ice templating the fibrils by a novel freezing procedure, which makes it possible to avoid the use of freeze-drying and subsequent crosslinking. Using colloidal probe atomic force microscopy adhesion measurements, hemiacetals were shown to be formed between the aldehyde-containing fibrils when they are brought into molecular contact, for example during ice templating. Hemiacetal crosslinked aerogels have been shaped and functionalised to demonstrate their application as biomimetic structural composites, electrical circuits and electrical cells. In addition, crosslinked, light-weight 3D fibre networks were prepared with á similar chemistry by a self-assembly process of pulp fibres. These networks could be dried under ambient conditions and the materials formed were wet-stable due to the hemiacetal crosslinks formed in the fibre–fibre contacts, which provided the networks with excellent mechanical properties and shape recovery capacity in water.

Finally, using a newly developed polyampholyte and mixing it with CNFs, heterofunctional composite films and aerogels could be prepared. By activating crosslinkable groups in these composite materials, they were able to undergo further water based chemical functionalisation. In this highly dispersed state, the composite could be irreversibly crosslinked by a hydrothermal treatment to create transparent, low solid content hydrogels.

Place, publisher, year, edition, pages
Stockholm: Kungliga Tekniska högskolan, 2019. p. 81
Series
TRITA-CBH-FOU ; 2019:44
National Category
Polymer Technologies Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-259346 (URN)978-91-7873-295-1 (ISBN)
Public defence
2019-10-11, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 37716-1
Note

QC 2019-09-13

Available from: 2019-09-13 Created: 2019-09-13 Last updated: 2019-09-13Bibliographically approved

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Erlandsson, JohanFrancon, HugoMarais, AndrewWågberg, Lars

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