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Synthesis, adsorption and adhesive properties of a cationic amphiphilic block copolymer for use as compatibilizer in composites
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer 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: 0000-0002-8194-0058
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), Chemistry, Surface and Corrosion Science.
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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.

Place, publisher, year, edition, pages
2012. Vol. 48, no 7, 1195-1204 p.
Keyword [en]
Adhesion, Amphiphilic, Block polymer, Cationic micelles, Cellulose, Compatibilizer
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-25243DOI: 10.1016/j.eurpolymj.2012.05.004ISI: 000306681200006Scopus ID: 2-s2.0-84862858693OAI: oai:DiVA.org:kth-25243DiVA: diva2:356725
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
In thesis
1. Surface modification of cellulose-based fibres for use in advanced materials
Open this publication in new window or tab >>Surface modification of cellulose-based fibres for use in advanced materials
2010 (English)Licentiate 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 fibres are combined with different types of polymers. There is hence a large need to develop efficient fibre modification techniques by which the fibres can be tailored to obtain specific properties. Furthermore, by modifying only the surface of fibers a significant change in properties can be achieved although only a relatively small amount of the total fibre material is modified. The potential impact of a surface modification increases tremendously when nano-sized fibres are used due to the larger interfacial area between the fibres and their surroundings. Interest in smaller building blocks in the nanometer range has continued to grow rapidly in recent years due to both the availability and preparation/synthesis of smaller building blocks and to the discovery of the high performance of these types of nanocomposites. In this thesis, three different types of surface modifications are presented as new tools to design the properties of new novel cellulose-based materials. In the first work, thermoresponsive nanocomposites have been assembled from specially designed thermoresponsive polymers and nanofibrillated cellulose. The polymers have one thermoresponsive block and one cationically charged block which can thus attach the polymer to an oppositely charged fibre/fibril surface. Multilayers were assembled with these polymers and the nanofibrillated cellulose utilizing the layer-by-layer technique, resulting in thin films with thermoresponsive behavior which for example could be used for controlled drug-release applications. In the second work, an amphiphilic block copolymer with one high molecular weight hydrophobic polystyrene block and one cationic block was synthesized for use as a compatibilizer between fibres and hydrophobic polymer matrices in composites. These polymers self-assemble into micelles in water with the hydrophobic part in the core of the micelle and the cationic part in the shell. Due to the cationic charges, these micelles adsorb to oppositely charged surfaces where the hydrophobic parts can be liberated on the surface by a heat treatment, leading to a new, less hydrophilic, surface with a contact angle close to that of pure polystyrene. Atomic force microscopy was used to measure the adhesive properties of a polymer-treated surface using a polystyrene probe at different temperatures and contact times. The adhesion increased with increasing contact time for the treated surfaces, probably due to entanglement between the polystyrene blocks at the treated surface and the probe. The relative increase in adhesion with contact time was higher at the lower temperature whereas the absolute value of the adhesion was higher at the higher temperature, most probably due to a larger molecular contact area. This odification technique could be utilized to make fibrebased composite materials with better mechanical properties. In the third work, click chemistry was used to covalently attach dendrons to cellulose surfaces and further to modify them with mannose groups to obtain specific interactions with  Concanavalin A. The protein interactions were studied at different protein concentrations with a quartz crystal microbalance. The multivalent dendronized surface showed a 10-fold increase in sensitivity to the protein compared to a monovalent reference surface. This could be used to design more sensitive cellulose-based biosensors in the future.

Abstract [sv]

Det finns idag en stor insikt av att vi behöver nya miljövänliga processer och produkter för att kunna skapa ett långsiktigt hållbart samhälle. Denna medvetenhet har stimulerat sökandet efter förnyelsebara, högkvalitativa material som kan ersätta oljebaserade produkter. I kombination med den ökande konkurrensen inom skogsindustrin, har detta stimulerat forskning inom olika typer av träbaserade material där cellulosarika fibrer kombineras med olika typer av polymerer så att vi använder vår förnyelsebara skogsråvara i så kallade högvärdesprodukter. Det finns därför ett stort behov av utveckling av effektiva tekniker för fibermodifiering där fibrer kan skräddarsys för att erhålla specifika egenskaper. Genom att endast modifiera fibrernas yta kan dessutom en markant förändring i egenskaper erhållas genom att endast modifiera en relativt liten del av det totala fibermaterialet. Den potentiella effekten av ytmodifiering ökar dessutom avsevärt när cellulosananofibriller används, eftersom gränsytan mellan fibrillerna och dess omgivning ökar dramatiskt när storleken minskar med flera tiopotenser. Intresset för mindre byggstenar i nanometerområdet har fortsatt att öka snabbt under de senaste åren, både tack vare tillgängligheten och ny teknik för tillverkning/syntes av mindre byggstenar, och insikter av de mycket goda egenskaper som den här typen av nanokompositer besitter. I föreliggande avhandling presenteras tre olika typer av fibermodifiering som kan användas som nya redskap för att skräddarsy egenskaper hos nya cellulosabaserade material. I det första arbetet har termoresponsiva nanokompositer byggts upp från specialtillverkade termoresponsiva polymerer och nanofibrillerad cellulosa. Polymererna har ett block som är termoresponsivt samt ett andra block som är katjoniskt laddat och därmed kan fästa polymeren till en motsatt laddad fiber/fibrillyta. Multiskikt byggdes upp med dessa polymer och den nanofibrillerade cellulosan genom att använda lager-på-lager tekniken, vilket resulterar i tunna filmer med termoresponsivt beteende som exempelvis skulle kunna användas för kontrollerad frisättning av läkemedel. I det andra arbetet har en amfifil block copolymer med ett högmolekulärt hydrofobt polystyrenblock och ett katjoniskt block syntetiserats för användning som kompatibilisator mellan fibrer och hydrofoba polymer matriser i fiber/fibrill förstärkta kompositer. Dessa polymerer självorganiseras i form av miceller i vatten med den hydrofoba delen i kärnan av micellen och den katjoniska delen i skalet. Eftersom micellerna har katjoniska laddningar adsorberar de till motsatt laddade ytor där de hydrofoba delarna kan frigöras på ytan efter en värmebehandling vilket leder till en ny, mindre vattenvätbar, yta. Ett atomkraftsmikroskop användes för att mäta de adhesiva egenskaperna mellan en polymerbehandlad yta och en polystyrenprob vid olika temperaturer och kontakttider. Adhesionen ökade med kontakttiden för de behandlade ytorna, troligtvis beroende på molekylär intrassling mellan polystyrenblock på den behandlade ytan och polystyrenproben. Den relativa adhesionsökningen, med ökad kontakttid, var högre vid den lägre temperaturen medan den absoluta adhesionskraften var högre vid den högre temperaturen, vilket troligen beror på en högre molekylär konataktyta vid den högre temperaturen. I det tredje arbetet användes klick-kemi för att kovalent fästa dendroner till cellulosaytor och vidare modifiera dem med mannosgrupper för att erhålla specifik växelverkan med Concanavalin A. Proteininteraktionerna studerades vid olika proteinkoncentrationer med hjälp av en kvartskristallmikrovåg. Den flervärda dendroniserade ytan visade en 10-faldig ökning i känslighet gentemot proteinet jämfört med den envärda referensytan. Detta skulle kunna användas för att skräddarsy känsligare cellulosabaserade biosensorer i framtiden.

Place, publisher, year, edition, pages
KTH, 2010. vii, 27 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:39
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-25245 (URN)978-91-7415-748-2 (ISBN)
Presentation
2010-10-14, V1, KTH, Teknikringen 76, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101014Available from: 2010-10-14 Created: 2010-10-13 Last updated: 2012-04-11Bibliographically approved
2. 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

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Carlmark, AnnaPettersson, TorbjörnMalmström, Eva E.Wågberg, Lars

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