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Control of wet adhesion between Layer-by-Layer covered surfaces by tailoring the structure and composition of the layers
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-5444-7276
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
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(English)Article in journal (Other academic) Submitted
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-102482OAI: oai:DiVA.org:kth-102482DiVA: diva2:553095
Note

QS 2012

Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2012-12-04Bibliographically approved
In thesis
1. Surface Modification of Cellulose-based Materials for Tailoring of Interfacial Interactions
Open this publication in new window or tab >>Surface Modification of Cellulose-based Materials for Tailoring of Interfacial Interactions
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The awareness of our need for a sustainable society has encouraged the search for renewable, high quality materials that can replace oil-based products. This, in combination with increased competition in the forest industry, has stimulated a lot of research into different types of wood-based materials where cellulose-rich fibers are combined with different types of polymers. There is hence a great need to develop efficient fiber modification techniques by which the fibers can be tailored to obtain specific properties. A significant change in properties can be achieved by modifying only the surface of fibers although only a relatively small amount of the total fiber material is modified. In this thesis, several surface modification techniques are presented as new tools to design the properties of different cellulose-based materials.

In paper I, thermoresponsive nanocomposites have been assembled from specially designed thermoresponsive block copolymers and nanofibrillated cellulose. The block copolymers have one thermoresponsive block and one cationically charged block which can thus attach the polymer to an oppositely charged fiber/fibril surface. Multilayers were assembled with these block copolymers and nanofibrillated cellulose (NFC) utilizing the Layer-by-Layer (LbL) technique, resulting in thin films with a thermoresponsive behavior.

In papers II and III, amphiphilic block copolymers with one less polar high molecular weight block and one cationic block were synthesized for use as a compatibilizer between fibers/fibrils and less polar polymer matrices in composites. The less polar block consisted of polystyrene (PS) in paper II and poly(ɛ-caprolactone) (PCL) in paper III. These polymers self-assemble into cationic micelles in water which can adsorb to oppositely charged surfaces, such as cellulose-based fibers/fibrils, in water under mild conditions and decrease the surface energy of the surface. Atomic force microscopy (AFM) was used to evaluate the adhesive properties of surfaces treated with these compatibilizers which clearly showed the formation of physical entanglements across the interfaces, which are essential for improved interfacial adhesion in the final composites. This modification technique could probably be utilized to make fiber-based composites with better mechanical properties. To be able to better compare this physical modification technique with a more traditional covalent grafting-from approach a method to measure attached amounts of grafted PCL onto cellulose model surfaces was developed in paper IV using a quartz crystal microbalance (QCM).

In paper V, multilayers of poly(allylamine hydrochloride) (PAH) and hyaluronic acid (HA) were assembled using the LbL technique and surface structure, build-up and adhesive behavior of the multilayers were evaluated. AFM force measurements showed that a significant adhesion even at long separation distances between two surfaces treated with PAH/HA multilayers could be achieved due to extensive interdiffusion across the interface during contact, leading to significant disentanglement during separation. Fundamental parameters contributing to improved adhesion for this type of system have been evaluated and this knowledge could be used to improve cellulose-based fiber networks and possibly also other types of cellulose-based materials.

In paper VI, click chemistry was used to covalently attach dendrons to cellulose surfaces and further modify them with mannose groups to obtain specific interactions with Concanavalin A. The protein interactions were studied at different protein concentrations with a QCM. The multivalent dendronized surface showed a 10-fold increase in sensitivity to the protein compared to a monovalent reference surface demonstrating greatly improved interfacial interactions. This approach could be used to improve interactions at different types of interfaces.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. viii, 53 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:37
National Category
Chemical Sciences Materials Chemistry Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-102368 (URN)978-91-7501-462-3 (ISBN)
Public defence
2012-10-05, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20120918

Available from: 2012-09-18 Created: 2012-09-14 Last updated: 2012-09-18Bibliographically approved
2. Tailoring fibre and paper properties using physical adsorption of polyelectrolytes
Open this publication in new window or tab >>Tailoring fibre and paper properties using physical adsorption of polyelectrolytes
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The adsorption of polyelectrolytes, both as monolayers and as multilayers, was investigated as an easy and non-expensive way of producing lignocellulosic fibrous materials with enhanced mechanical properties.

In the first part of the work described in this thesis, the adsorption of a polyelectrolyte monolayer onto the surface of unbleached and unbeaten kraft pulp fibres with different kappa numbers was investigated. Adsorption isotherms were obtained in order to determine the amounts of polymer that could be adsorbed by the different pulps. Handsheets were made from the treated fibres and the mechanical properties were studied. The results showed that the use of only 2 mg/g of a polymeric amine such as polyallylamine or polyvinylamine could under certain conditions increase the tensile strength index by up to 50 %.

In a second investigation, the Layer-by-Layer deposition technique was used to build up polyelectrolyte multilayers on the surfaces of bleached kraft pulp fibres. Two systems were studied and the presence of added salt in the systems was also investigated. The results showed that the system composed of polyallylamine hydrochloride and hyaluronic acid provided a dramatic increase in both strength (from 20 Nm/g to 70 Nm/g) and strain at break (from 2.0 % to 6.5 %) with only five deposited bilayers. Such a stretchability could make this material very suitable for 3D-forming of packaging materials.

The behaviour of this polyallylamine/hyaluronic acid system was then studied from a more fundamental point of view in a third study in order to determine the mechanisms on the nano-scale behind the large improvements observed on the macroscopic paper scale. A quartz crystal microbalance equipment was used to study the adsorption onto model surfaces and show the superlinear trend of the build-up. Atomic force microscopy was also used to study the structural changes occurring upon adsorption of each polymeric layer as well as the adhesive properties of the system.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. viii, 37 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:62
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-106222 (URN)978-91-7501-557-6 (ISBN)
Presentation
2012-12-07, K1, Teknikringen 56, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20121204

Available from: 2012-12-04 Created: 2012-11-30 Last updated: 2012-12-04Bibliographically approved

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