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Surface Modification of Cellulose by Covalent Grafting and Physical Adsorption for Biocomposite Applications
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is an increasing interest to replace fossil-based materials with renewable alternatives. Cellulose fibers/nanofibrils (CNF) are sustainable options since they are biobased and biodegradable. In addition, they combine low weight with high strength; making them suitable to, for example, reinforce composites. However, to be able to use them as such, modifications are often necessary. This study therefore aimed at modifying cellulose fibers, model surfaces of cellulose and CNF. Cellulose fibers and CNF were thereafter incorporated into composite materials and evaluated.

Surface-initiated ring-opening polymerization (SI-ROP) was performed to graft ε-caprolactone (ε-CL) from cellulose fibers. From these fibers, paper-sheet biocomposites were produced that could form laminate structures without the need for any addition of matrix polymer.

By combining ROP and atom transfer radical polymerization (ATRP), diblock copolymers of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and PCL were prepared. Quaternized (cationic) PDMAEMA, allowed physical adsorption of block copolymers onto anionic surfaces, and, thereby, alteration of surface energy and adhesion to a potential matrix. Furthermore, the architecture of block copolymers of PCL and PDMAEMA was varied to investigate effects on morphology/crystallinity and adsorption behavior. In addition, poly(butadiene) was also evaluated as the hydrophobic block in the form of cationic and anionic triblock copolymers.

Polystyrene (PS) was covalently grafted from CNF and used as reinforcement in PS-based composites. In an attempt to determine stress transfer from matrix to CNF, a method based on Raman spectroscopy was utilized.

Covalent grafting and physical adsorption of PCL from/onto CNF were compared by incorporating modified CNF in PCL matrices. Both approaches resulted in improved mechanical properties compared to unmodified CNF, but even at low amounts of modified CNF, covalent grafting gave tougher materials and indicated higher interfacial adhesion.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , 89 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:49
National Category
Polymer Technologies Paper, Pulp and Fiber Technology
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-155920ISBN: 978-91-7595-322-9 (print)OAI: oai:DiVA.org:kth-155920DiVA: diva2:763426
Public defence
2014-12-05, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20141117

Available from: 2014-11-17 Created: 2014-11-14 Last updated: 2014-11-17Bibliographically approved
List of papers
1. Paper-sheet biocomposites based on wood pulp grafted with poly(ε-caprolactone)
Open this publication in new window or tab >>Paper-sheet biocomposites based on wood pulp grafted with poly(ε-caprolactone)
(English)Manuscript (preprint) (Other academic)
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-155922 (URN)
Note

QS 2014

Available from: 2014-11-14 Created: 2014-11-14 Last updated: 2014-11-17Bibliographically approved
2. Physical tuning of cellulose-polymer interactions utilizing cationic block copolymers based on PCL and quaternized PDMAEMA
Open this publication in new window or tab >>Physical tuning of cellulose-polymer interactions utilizing cationic block copolymers based on PCL and quaternized PDMAEMA
Show others...
2012 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, no 12, 6796-6807 p.Article in journal (Refereed) Published
Abstract [en]

In this work, the objective was to synthesize and evaluate the properties of a compatibilizer based on poly(ε-caprolactone) aimed at tuning the surface properties of cellulose fibers used in fiber-reinforced biocomposites. The compatibilizer is an amphiphilic block copolymer consisting of two different blocks which have different functions. One block is cationic, quaternized poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and can therefore electrostatically attach to anionic reinforcing materials such as cellulose-based fibers/fibrils under mild conditions in water. The other block consists of poly(ε-caprolactone) (PCL) which can decrease the surface energy of a cellulose surface and also has the ability to form physical entanglements with a PCL surface thereby improving the interfacial adhesion. Atom Transfer Radical Polymerization (ATRP) and Ring-Opening Polymerization (ROP) were used to synthesize three block copolymers with the same length of the cationic PDMAEMA block but with different lengths of the PCL blocks. The block copolymers form cationic micelles in water which can adsorb to anionic surfaces such as silicon oxide and cellulose-model surfaces. After heat treatment, the contact angles of water on the treated surfaces increased significantly, and contact angles close to those of pure PCL were obtained for the block copolymers with longer PCL blocks. AFM force measurements showed a clear entangling behavior between the block copolymers and a PCL surface at about 60 C, which is important for the formation of an adhesive interface in the final biocomposites. This demonstrates that this type of amphiphilic block copolymer can be used to improve interactions in biocomposites between anionic reinforcing materials such as cellulose-based fibers/fibrils and less polar matrices such as PCL.

Keyword
biocomposite, block copolymer, cationic micelle, cellulose, compatibilizer, poly(ε-caprolactone)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-116785 (URN)10.1021/am301981r (DOI)000313149800054 ()2-s2.0-84871658132 (Scopus ID)
Note

QC 20130128

Available from: 2013-01-28 Created: 2013-01-28 Last updated: 2017-12-06Bibliographically approved
3. Well-defined ABA- and BAB-type block copolymers of PDMAEMA and PCL
Open this publication in new window or tab >>Well-defined ABA- and BAB-type block copolymers of PDMAEMA and PCL
Show others...
2014 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 49, 25809-25818 p.Article in journal (Refereed) Published
Abstract [en]

Triblock copolymers of ABA- and BAB-type consisting of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, A) and poly(epsilon-caprolactone) (PCL, B) have successfully been prepared. PDMAEMA-b-PCL-b-PDMAEMA (ABA) and PCL-b-PDMAEMA-b-PCL (BAB) were synthesised by a combination of ring-opening polymerisation of epsilon-CL, atom transfer radical polymerisation of DMAEMA and end-group conversion, performed through either acylation or azide-alkyne "click" chemistry. All samples were analysed by size exclusion chromatography where it was found that the evaluation of PDMAEMA-containing polymers was difficult due to the thermoresponsivity of PDMAEMA, affecting the solubility of the polymer in the temperature range at which the SEC was operated. From differential scanning calorimetry measurements it was shown that the crystallinity could be altered by changing the order of the blocks; with PDMAEMA as the outer block (ABA), the inherent crystallinity of PCL was destroyed while with PCL as the outer block (BAB), the degree of crystallinity was in the same proximity as for a PCL homopolymer.

Keyword
Block copolymers, Differential scanning calorimetry, 2-(dimethylamino)ethyl methacrylate, Caprolactone, Crystallinities, Degree of crystallinity, End groups, Ring opening, Synthesised, Temperature range
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-148652 (URN)10.1039/c4ra04325a (DOI)000338434500041 ()2-s2.0-84902954199 (Scopus ID)
Note

QC 20150624

Available from: 2014-08-11 Created: 2014-08-11 Last updated: 2017-12-05Bibliographically approved
4. Bionanocomposites reinforcedwith cellulose nanofibrils compatibilized through covalent grafting or physisorption of PCL –a comparative study
Open this publication in new window or tab >>Bionanocomposites reinforcedwith cellulose nanofibrils compatibilized through covalent grafting or physisorption of PCL –a comparative study
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-155923 (URN)
Note

QS 2014

Available from: 2014-11-14 Created: 2014-11-14 Last updated: 2014-11-17Bibliographically approved

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