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On the mechanism behind freezing-induced chemical crosslinking in ice-templated cellulose nanofibril aerogels
KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.ORCID-id: 0000-0003-1874-2187
KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.ORCID-id: 0000-0002-5444-7276
KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.ORCID-id: 0000-0002-9486-5288
Visa övriga samt affilieringar
2018 (Engelska)Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, nr 40, s. 19371-19380Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The underlying mechanism related to freezing-induced crosslinking of aldehyde-containing cellulose nanofibrils (CNFs) has been investigated, and the critical parameters behind this process have been identified. The aldehydes introduced by periodate oxidation allows for formation of hemiacetal bonds between the CNFs provided the fibrils are in sufficiently close contact before the water is removed. This is achieved during the freezing process where the cellulose components are initially separated, and the growth of ice crystals forces the CNFs to come into contact in the thin lamellae between the ice crystals. The crosslinked 3-D structure of the CNFs can subsequently be dried under ambient conditions after solvent exchange and still maintain a remarkably low density of 35 kg m-3, i.e. a porosity greater than 98%. A lower critical amount of aldehydes, 0.6 mmol g-1, was found necessary in order to generate a crosslinked 3-D CNF structure of sufficient strength not to collapse during the ambient drying. The chemical stability of the 3-D structure can be further enhanced by converting the hemiacetals to acetals by treatment with an alcohol under acidic conditions.

Ort, förlag, år, upplaga, sidor
Royal Society of Chemistry , 2018. Vol. 6, nr 40, s. 19371-19380
Nyckelord [en]
Aerogels, Aldehydes, Cellulose, Chemical stability, Crosslinking, Freezing, Nanofibers, Acidic conditions, Ambient conditions, Cellulose nanofibrils (CNFs), Chemical cross-linking, Freezing process, Lower critical, Periodate oxidation, Solvent exchanges, Ice
Nationell ämneskategori
Polymerteknologi
Identifikatorer
URN: urn:nbn:se:kth:diva-247488DOI: 10.1039/c8ta06319bISI: 000448413100008Scopus ID: 2-s2.0-85055128762OAI: oai:DiVA.org:kth-247488DiVA, id: diva2:1302742
Anmärkning

QC 20190405

Tillgänglig från: 2019-04-05 Skapad: 2019-04-05 Senast uppdaterad: 2019-09-13Bibliografiskt granskad
Ingår i avhandling
1. CONTROLLED ASSEMBLY AND FUNCTIONALISATION OF CELLULOSE-BASED MATERIALS
Öppna denna publikation i ny flik eller fönster >>CONTROLLED ASSEMBLY AND FUNCTIONALISATION OF CELLULOSE-BASED MATERIALS
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: Kungliga Tekniska högskolan, 2019. s. 81
Serie
TRITA-CBH-FOU ; 2019:44
Nationell ämneskategori
Polymerteknologi Pappers-, massa- och fiberteknik
Forskningsämne
Fiber- och polymervetenskap
Identifikatorer
urn:nbn:se:kth:diva-259346 (URN)978-91-7873-295-1 (ISBN)
Disputation
2019-10-11, F3, Lindstedtsvägen 26, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Forskningsfinansiär
Energimyndigheten, 37716-1
Anmärkning

QC 2019-09-13

Tillgänglig från: 2019-09-13 Skapad: 2019-09-13 Senast uppdaterad: 2019-10-04Bibliografiskt granskad

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Erlandsson, JohanPettersson, TorbjörnIngverud, TobiasLarsson, Per A.Malkoch, MichaelWågberg, Lars

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Erlandsson, JohanPettersson, TorbjörnIngverud, TobiasLarsson, Per A.Malkoch, MichaelWågberg, Lars
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FiberteknologiFiber- och polymerteknologiWallenberg Wood Science CenterYtbehandlingsteknikVinnExcellens Centrum BiMaC Innovation
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Journal of Materials Chemistry A
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