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Thermoresponsive nanocomposites from multilayers of nanofibrillated cellulose and specially designed N-isopropylacrylamide based polymers
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-8348-2273
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-8194-0058
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0001-8622-0386
2010 (English)In: Soft Matter, ISSN 1744-683X, Vol. 6, no 2, 342-352 p.Article in journal (Refereed) Published
Abstract [en]

In this work positively charged polymers based on N-isopropylacrylamide (NIPAAm) have been synthesised and investigated in solution, on surfaces and in polyelectrolyte multilayers (PEMs) in combination with nanofibrillated cellulose (NFC). Polymers having thermoresponsive properties at low salt concentrations in solution and when adsorbed onto surfaces were obtained by separating the charged groups from the thermoresponsive part in different blocks within the polymer. The polymers have been synthesised using atom transfer radical polymerisation (ATRP) of NIPAAm and (3-acrylamidopropyl)trimethylammonium chloride (APTAC), which is the cationic monomer. All the block copolymers exhibited a lower critical solution temperature (LCST) in water between 35 and 39 degrees C and a positive correlation was found between the LCST and the charge densities of the polymers. It is shown that electrostatic interactions control the adsorption of the prepared polyelectrolytes to SiO2 surfaces and that the block copolymers are thermoresponsive when adsorbed at the solid-liquid interface. PEMs were also assembled with the synthesised polymers and NFC which is a renewable, fibrillar nanomaterial with interesting strength and biocompatibility properties. Even more interestingly it has been found that the formation of the layer-by-layer (LbL) structures of NFC and the block copolymers were demonstrated to have thermal responsivity. This type of thermoresponsive nanocomposite could be used as nano-containers for controlled release or for example in membranes where the permeability could be controlled by the temperature.

Place, publisher, year, edition, pages
2010. Vol. 6, no 2, 342-352 p.
Keyword [en]
quartz-crystal microbalance, living radical polymerization, polyelectrolyte multilayers, responsive polymers, microfibrillated, cellulose, gene delivery, poly(n-isopropylacrylamide), adsorption, temperature, transition
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-19111DOI: 10.1039/b910481jISI: 000273576800019ScopusID: 2-s2.0-77954539174OAI: diva2:337158

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2016-04-20Bibliographically 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.
Trita-CHE-Report, ISSN 1654-1081 ; 2012:37
National Category
Chemical Sciences Materials Chemistry Polymer Chemistry
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)

QC 20120918

Available from: 2012-09-18 Created: 2012-09-14 Last updated: 2012-09-18Bibliographically approved

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Utsel, SimonMalmström, Eva E.Carlmark, AnnaWågberg, Lars
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