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Supramolecular double networks of cellulose nanofibrils and algal polysaccharides with excellent wet mechanical properties
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0003-4388-8970
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0002-9572-6888
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0001-8622-0386
2018 (English)In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 20, no 11, p. 2558-2570Article in journal (Refereed) Published
Abstract [en]

Supramolecular double network films, consisting of cellulose nanofibrils (CNF) entangled with the algal polysaccharides alginate or carrageenan, were prepared using a rapid vacuum filtration process to achieve water-resistant CNF nanopapers with excellent mechanical properties in both the wet and dry states following the locking of the structures using Ca2+. The rigid network of calcium alginate was more efficient than the more flexible network of calcium carrageenan and 10% by weight of alginate was sufficient to form a network that suppressed the swelling of the CNF film by over 95%. The resulting material could be compared to a stiff rubber with a Young's modulus of 135 MPa, a tensile strength of 17 MPa, a strain-at-break above 55%, and a work of fracture close to 5 MJ m(-3) in the wet state, which was both significantly stronger and more ductile than the calcium-treated CNF reference nanopaper. It was shown that the state in which Ca2+ was introduced is crucial, and it is also hypothesized that the alginate works as a sacrificial network that prevents the CNF from aligning during loading and that this leads to the increased toughness. The material maintained its barrier properties at elevated relative humidities and the extensibility and ductility made possible hygroplastic forming into three-dimensional shapes. It is suggested that the attractive force in the CNF part of the double network in the presence of multivalent ions is due to the ion-ion correlation forces generated by the fluctuating counter-ion cloud, since no significant ion coordination was observed using FTIR.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY , 2018. Vol. 20, no 11, p. 2558-2570
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-231187DOI: 10.1039/c8gc00590gISI: 000434313100018Scopus ID: 2-s2.0-85048040852OAI: oai:DiVA.org:kth-231187DiVA, id: diva2:1233564
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20180718

Available from: 2018-07-18 Created: 2018-07-18 Last updated: 2019-04-08Bibliographically approved
In thesis
1. Design of Cellulose-based Materials by Supramolecular Assemblies
Open this publication in new window or tab >>Design of Cellulose-based Materials by Supramolecular Assemblies
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Due to climate change and plastic pollution, there is an increasing demand for bio-based materials with similar properties to those of common plastics yet biodegradable. In this respect, cellulose is a strong candidate that is already being refined on a large industrial scale, but the properties differ significantly from those of common plastics in terms of shapeability and water-resilience.

This thesis investigates how supramolecular interactions can be used to tailor the properties of cellulose-based materials by modifying cellulose surfaces or control the assembly of cellulose nanofibrils (CNFs). Most of the work is a fundamental study on interactions in aqueous environments, but some material concepts are presented and potential applications are discussed.

The first part deals with the modification of cellulose by the spontaneous adsorption of xyloglucan or polyelectrolytes. The results indicate that xyloglucan adsorbs to cellulose due to the increased entropy of water released from the surfaces, which is similar to the increased entropy of released counter-ions that drives polyelectrolyte adsorption. The polyelectrolyte adsorption depends on the charge of the cellulose up to a limit after which the charge density affects only the first adsorbed layer in a multilayer formation.

Latex nanoparticles with polyelectrolyte coronas can be adsorbed onto cellulose in order to prepare hydrophobic cellulose surfaces with strong and ductile wet adhesion, provided the glass transition of the core is below the ambient temperature.

The second part of the thesis seeks to explain the interactions between different types of cellulose nanofibrils in the presence of different ions, using a model consisting of ion-ion correlation and specific ion effects, which can be employed to rationally design water-resilient and transparent nanocellulose films. The addition of small amounts of alginate also creates interpenetrating double networks, and these networks lead to a synergy which improves both the stiffness and the ductility of the films in water.

A network model has been developed to understand these materials, with the aim to explain the properties of fibril networks, based on parameters such as the aspect ratio of the fibrils, the solidity of the network, and the ion-induced interactions that increase the friction between fibrils. With the help of this network model and the model for ion-induced interactions, we have created films with wet-strengths surpassing those of common plastics, or a ductility suitable for hygroplastic forming into water-resilient and biodegradable packages. Due to their transparency, water content, and the biocompatibility of cellulose, these materials are also suitable for biomaterial or bioelectronics applications. 

Abstract [sv]

På grund av klimatförändringar och ständigt ökande plastföroreningar finns det en växande efterfrågan på biobaserade material med egenskaper som liknar dem hos vanliga plaster och som samtidigt är biologiskt nedbrytbara. I detta avseende är cellulosa är en stark kandidat som redan framställs i stor industriell skala, men egenskaperna skiljer sig markant från plasternas med avseende på formbarhet och vattentålighet.

Denna avhandling undersöker hur supramolekylära interaktioner kan användas för att skräddarsy egenskaperna hos cellulosa-baserade material genom att modifiera cellulosaytor eller styra hur cellulosa nanofibriller (CNFs) sätts samman. Huvuddelen av arbetet berör grundläggande studier kring interaktioner i vatten, men några materialkoncept och potentiella tillämpningar diskuteras.

Den första delen avhandlar hur spontan adsorption av xyloglukan eller polyelektrolyter kan användas för att modifiera cellulosa. Resultaten indikerar att xyloglukan adsorberar till cellulosa på grund av den ökade entropin hos vatten som frigörs från ytorna, vilket liknar den ökade entropin hos frigjorda motjoner som driver polyelektrolytadsorption. Adsorptionen av polyeletrolyter beror på cellulosans laddning upp till en viss gräns, varefter laddningstätheten endast påverkar adsorptionen i första lagret i en multilager formering.

Adsorption av latexnanopartiklar med en korona av polyeletrolyter, ger hydrofoba cellulosaytor med stark och töjbar, våt vidhäftning, om kärnans glasövergång sker vid lägre temperatur än omgivningens.

Syftet med den andra delen av avhandlingen är att förklara interaktioner mellan olika typer av cellulosa nanofibriller i närvaro av olika joner. Detta görs med en modell bestående av jon-jonkorrelation och specifika joneffekter, som kan användas för rationell design av vattentåliga och transparenta filmer av nanocellulosa. Tillsatsen av små mängder alginat skapar också interpenetrerande dubbla nätverk, och dessa nätverk leder till en synergi som förbättrar både styvheten och töjbarheten hos filmerna i vatten.

En nätverksmodell utvecklades för att förstå dessa material. Modellen klarar av att förklara hur egenskaperna hos fibrillnätverk beror av parametrar som fibrillernas geometri, nätverkets soliditet och friktionen som induceras av specifika joner. Med hjälp av nätverksmodellen och modellen för joninducerade interaktioner kan vi skapa filmer med våtstyrka som överträffar den hos många plaster, eller med en töjbarhet som är lämplig för hygroplastisk formpressning till vattentåliga och biologiskt nedbrytbara förpackningar. Filmernas transparens och vatteninnehåll, samt biokompatibiliteten hos cellulosa, gör dem lämpliga som biomaterial eller för bioelektronikapplikationer.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 66
Series
TRITA-CBH-FOU ; 2019:19
Keywords
Adhesion, adsorption, alginate, assemblies, biodegradable, biomaterials, biopolymers, cellulose, cellulose nanofibrils, CNFs, gas barrier, hemicellulose, interfaces, ion-ion correlation, latex, layer-by-layer, metal-ligand complexes, montmorillonite, multivalent ions, packaging, PISA, polyelectrolyte multilayers, polyelectrolytes, polysaccharides, RAFT, renewable, specific ion effects, supramolecular, surfaces, sustainable, thin films, water-resilient, xyloglucan
National Category
Chemical Sciences Materials Chemistry Polymer Chemistry Physical Chemistry Nano Technology Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-248046 (URN)978-91-7873-161-9 (ISBN)
Public defence
2019-05-10, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20190411

Available from: 2019-04-11 Created: 2019-04-03 Last updated: 2019-04-11Bibliographically approved

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Benselfelt, TobiasEngström, JoakimWågberg, Lars

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