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Thermoresponsive cryogels reinforced with cellulose nanocrystals
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.ORCID iD: 0000-0002-3755-722X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.ORCID iD: 0000-0002-8348-2273
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.ORCID iD: 0000-0002-8194-0058
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Herein, we report the first study of thermoresponsive cryogels with cellulose nanocrystals (CNCs) incorporated into the structure. Free radical polymerization was utilized to synthesize cryogels of poly(N-isopropylacrylamide) (PNIPAAm), resulting in thermoresponsive gels after the cryo-polymerization. Two types of CNCs were investigated: one which had reactive vinyl groups on the surface, enabling covalent incorporation and crosslinking with the cryogel network; and one which had no reactive groups on the surface, rendering it physically embedded in the network. The degree of crosslinking of the cryogels was controlled by varying the addition of N,N´-methylenebisacrylamide (MBAm). The cryogels were analyzed by FE-SEM and were all found to be macroporous. The morphology of the gels was largely dependent on the reaction conditions and the presence of CNC. The swelling properties of the freeze-dried gels were investigated and all gels exhibited a thermoresponsive behavior. Our study showed that the incorporation of CNCs is an effective method to alter both the morphologies and the mechanical properties of a cryogel, although the final properties of the cryogels depend on several different parameters. Due to the complexity of the system, a clear trend regarding the CNC incorporation is difficult to conclude, but compression testing showed that a cryogel having 1 wt% of crosslinkable CNC was far superior to the other gels in terms of mechanical properties, exhibiting that the presence of crosslinkable groups on the surface of CNCs could have a large influence over the final properties.

National Category
Polymer Technologies
URN: urn:nbn:se:kth:diva-172931OAI: diva2:850777

QS 2015

Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2015-09-02Bibliographically approved
In thesis
1. Thermoresponsive cellulose-based composites by polymer modification
Open this publication in new window or tab >>Thermoresponsive cellulose-based composites by polymer modification
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interest in utilizing cellulose based materials has grown rapidly in recent years, due to the growing environmental concerns about utilizing fossil based material. One potential application of cellulose is in thermoresponsive materials, which are attracting attention due to their ability of altering conformation when exposed to changes in external temperature. In this study, a variation of cellulose substrates have been utilized; both as the main component and as reinforcing fillers in thermoresponsive composites.

Photoinduced controlled radical polymerization was utilized to graft the thermoresponsive polymer poly(di(ethylene glycol) ethyl ether acrylate) (PDEGA)  from the surface of filter paper. The method showed to be efficient to graft large amounts of polymer from the cellulose surface in short reaction times, while utilizing smaller amounts of catalyst than typically employed in controlled radical polymerizations.

Di-, tri, and star block copolymers of quaternized poly(2-(dimethylamino)ethyl methacrylate) (qPDMAEMA) and poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) were synthesized by atom transfer radical polymerization (ATRP), and adsorbed to cellulose nanofibrils (CNFs) in a water dispersion. This provided a simple route for the preparation of thermoresponsive CNF based composites.

Thermoresponsive cryogels of poly(N-isopropylacrylamide) (PNIPAAm), synthesized by free radical polymerization (FRP), were reinforced by the addition of cellulose nanocrystals (CNCs). Two types of CNCs were investigated: neat CNC and CNC with acrylic, polymerizable,  groups attached to its structure. The CNC addition showed to be an efficient way to modify the mechanical properties of the cryogels.

All materials synthesized in this project displayed thermoresponsive properties. Cellulose can therefore be considered to be a promising material for the production of more environmentally friendly thermoresponsive composites.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 54 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:44
National Category
Polymer Technologies
Research subject
Chemical Engineering
urn:nbn:se:kth:diva-172828 (URN)978-7595-654-1 (ISBN)
Public defence
2015-09-25, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20150902

Available from: 2015-09-02 Created: 2015-08-31 Last updated: 2015-09-02Bibliographically approved

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Larsson, EmmaBoujemaoui, AssyaMalmström, EvaCarlmark, Anna
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