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Surface Modification of Cellulose-based Materials for Tailoring of Interfacial Interactions
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.
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: urn:nbn:se:kth:diva-102368ISBN: 978-91-7501-462-3 (print)OAI: oai:DiVA.org:kth-102368DiVA: diva2:552487
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
List of papers
1. Thermoresponsive nanocomposites from multilayers of nanofibrillated cellulose and specially designed N-isopropylacrylamide based polymers
Open this publication in new window or tab >>Thermoresponsive nanocomposites from multilayers of nanofibrillated cellulose and specially designed N-isopropylacrylamide based polymers
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.

Keyword
quartz-crystal microbalance, living radical polymerization, polyelectrolyte multilayers, responsive polymers, microfibrillated, cellulose, gene delivery, poly(n-isopropylacrylamide), adsorption, temperature, transition
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-19111 (URN)10.1039/b910481j (DOI)000273576800019 ()2-s2.0-77954539174 (Scopus ID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2016-04-20Bibliographically approved
2. Synthesis, adsorption and adhesive properties of a cationic amphiphilic block copolymer for use as compatibilizer in composites
Open this publication in new window or tab >>Synthesis, adsorption and adhesive properties of a cationic amphiphilic block copolymer for use as compatibilizer in composites
Show others...
2012 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 48, no 7, 1195-1204 p.Article in journal (Refereed) Published
Abstract [en]

In this work, the objective was to synthesize a compatibilizer that can electrostatically adsorb onto cellulose fibers, in fiber-based composites, to enhance the interaction between the fibers and non-polar polymer matrices. This physical route to attach the compatibilizer onto and thereby modify a fiber surface is convenient since it can be performed in water under mild conditions. Polystyrene (PS) was used for the high molecular weight, non-polar, block and poly(dimethylamino)ethyl methacrylate (PDMAEMA) was used as the polar block, which was subsequently quaternized to obtain cationic charges. The block copolymer self-assembles in water into cationic micelles and the adsorption to both silicon oxide surfaces and cellulose model surfaces was studied. The micelles spread out on the surface after heat treatment and contact angle measurements showed that the contact angles against water increased significantly after this treatment. AFM force measurements were performed with a PS probe to study the adhesive properties. The adhesion increased with increasing contact time for the treated surfaces, probably due to entanglements between the polystyrene blocks at the treated surface and the probe. This demonstrates that the use of this type of amphiphilic block copolymer is a promising route to improve the compatibility between charged reinforcing materials, such as cellulose-based fibers/fibrils, and hydrophobic matrices in composite materials.

Keyword
Adhesion, Amphiphilic, Block polymer, Cationic micelles, Cellulose, Compatibilizer
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-25243 (URN)10.1016/j.eurpolymj.2012.05.004 (DOI)000306681200006 ()2-s2.0-84862858693 (Scopus ID)
Note

QC 20120810. Updated from manuscript to article in journal.

Available from: 2010-10-13 Created: 2010-10-13 Last updated: 2017-12-12Bibliographically approved
3. Physical tuning of cellulose/polymer interactions utilizing cationic block copolymers based on poly(ε-caprolactone)
Open this publication in new window or tab >>Physical tuning of cellulose/polymer interactions utilizing cationic block copolymers based on poly(ε-caprolactone)
Show others...
(English)Article in journal (Other academic) Submitted
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-102478 (URN)
Note

QS 2012

Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2012-09-18Bibliographically approved
4. Surface-initiated ring-opening polymerization from cellulose model surfaces monitored by a Quartz Crystal Microbalance
Open this publication in new window or tab >>Surface-initiated ring-opening polymerization from cellulose model surfaces monitored by a Quartz Crystal Microbalance
Show others...
2012 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 2, 512-517 p.Article in journal (Refereed) Published
Abstract [en]

Polymer surface-grafting is an excellent method to modify the properties of a surface. However, surface-initiated polymerization is still relatively poorly understood due to the lack of appropriate characterization methods and tools to monitor the polymerizations. Herein, we report the in situ, surface-initiated ring-opening polymerization (SI-ROP) investigated in real time by the Quartz Crystal Microbalance (QCM) technique. The polymerization was performed from a cellulose model surface and the polymerization was initiated directly from the available hydroxyl groups on the cellulose. The cyclic monomer 3-caprolactone and an organic catalyst, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), were used, and the reaction was performed in bulk at room temperature. Since a free polymer was formed in bulk in parallel to the grafting from the surface, the reaction was performed in three cycles with rinsing steps in between to measure only the effect of the surface grafting. The change in frequency showed that the grafted amount of polymer increased after each cycle indicating that most of the chain ends remained active. After polymer grafting, the cellulose model surface showed a more hydrophobic character, and the surface roughness of the cellulose model surface was reduced. This study clearly shows that QCM is a viable method to monitor SI-ROP in situ from cellulose surfaces. We believe this is an important step towards a deeper understanding of how to tailor the interface between polymer-modified cellulose and a polymer matrix in biocomposites.

National Category
Chemical Engineering Physical Sciences
Identifiers
urn:nbn:se:kth:diva-93406 (URN)10.1039/c1sm06121f (DOI)000301791100035 ()2-s2.0-83455205987 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20120416Available from: 2012-04-16 Created: 2012-04-16 Last updated: 2017-12-07Bibliographically approved
5. Control of wet adhesion between Layer-by-Layer covered surfaces by tailoring the structure and composition of the layers
Open this publication in new window or tab >>Control of wet adhesion between Layer-by-Layer covered surfaces by tailoring the structure and composition of the layers
Show others...
(English)Article in journal (Other academic) Submitted
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-102482 (URN)
Note

QS 2012

Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2012-12-04Bibliographically approved
6. Bifunctional Dendronized Cellulose Surfaces as Biosensors
Open this publication in new window or tab >>Bifunctional Dendronized Cellulose Surfaces as Biosensors
Show others...
2011 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 6, 2114-2125 p.Article in journal (Refereed) Published
Abstract [en]

Well-defined dendronized cellulose substrates displaying multiple representations of dual-functionality were constructed by taking advantage of the efficiency of the click reaction combined with traditional anhydride chemistry. First, activated cellulose surfaces were decorated with several generations of dendrons, and their peripheral reactive groups were subsequently reacted with a trifunctional orthogonal monomer. The generated substrate tool box was successfully explored by accurately tuning the surface function using a versatile orthogonal dual postfunctionalization approach. In general, the reactions were monitored by using a click-dye reagent or a quartz crystal microbalance (QCM) technique, and the resulting surfaces were well-characterized using XPS, and contact angle measurements. Utilizing this approach two different surfaces have been obtained; that is, triethylenglycol oligomers and amoxicillin molecules were efficiently introduced to the dendritic surface. As a second example, mannose-decorated hydroxyl functional surfaces illustrated their potential as biosensors by multivalent detection of lectin protein at concentration as low as 5 nM.

Keyword
CLICK-CHEMISTRY, EFFICIENT SYNTHESIS, FUTURE-DIRECTIONS, DENDRIMERS, AZIDE, FILMS
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-35633 (URN)10.1021/bm200201y (DOI)000291499900019 ()2-s2.0-79958779836 (Scopus ID)
Funder
Swedish Research Council, 2006-3617Swedish Research Council, 2009-3259
Note
QC 20110704Available from: 2011-07-04 Created: 2011-07-04 Last updated: 2017-12-11Bibliographically approved

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