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Facile Preparation Route for Nanostructured Composites: Surface-Initiated Ring-Opening Polymerization of epsilon-Caprolactone from High-Surface-Area Nanopaper
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-3755-722X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-8348-2273
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2012 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, no 6, 3191-3198 p.Article in journal (Refereed) Published
Abstract [en]

In this work, highly porous nanopaper, i.e., sheets of papers made from non-aggregated nanofibrillated cellulose (NFC), have been surface-grafted with poly(epsilon-caprolactone) (PCL) by surface-initiated ring-opening polymerization (SI-ROP). The nanopaper has exceptionally high surface area (similar to 300 m(2)/g). The "grafting from" of the nanopapers was compared to "grafting from" of cellulose in the form of filter paper, and in both cases either titanium n-butoxide (Ti(On-Bu)(4)) or tin octoate (Sn(Oct)(2)) was utilized as a catalyst. It was found that a high surface area leads to significantly higher amount of grafted PCL in the substrates when Sn(Oct)2 was utilized as a catalyst. Up to 79 wt % PCL was successfully grafted onto the nanopapers as compared to filter paper where only 2-3 wt % PCL was grafted. However, utilizing Ti(On-Bu)4 this effect was not seen and the grafted amount was essentially similar, irrespectively of surface area. The mechanical properties of the grafted nanopaper proved to be superior to those of pure PCL films, especially at elevated temperatures. The present bottom-up preparation route of NFC-based composites allows high NFC content and provides excellent nanostructural control. This is an important advantage compared with some existing preparation routes where dispersion of the filler in the matrix is challenging.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2012. Vol. 4, no 6, 3191-3198 p.
Keyword [en]
ring-opening polymerization, nanofibrillated cellulose, nanopaper, surface grafting, high surface area
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:kth:diva-99242DOI: 10.1021/am300537hISI: 000305716900052Scopus ID: 2-s2.0-84863198035OAI: oai:DiVA.org:kth-99242DiVA: diva2:541833
Note

QC 20160324

Available from: 2012-07-24 Created: 2012-07-23 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Surface Modification of Cellulose by Covalent Grafting and Physical Adsorption
Open this publication in new window or tab >>Surface Modification of Cellulose by Covalent Grafting and Physical Adsorption
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interest in new environmentally friendly cellulose‐based productshas increased tremendously over the last years. At the same time theSwedish forest industry faces new challenges in its strive to increase the utilization of cellulose fibers in high‐value end‐products. The aim of this study was to expand the toolbox for surface modification of cellulose byemploying covalent surface‐initiated (SI) polymerizations or by physicaladsorption of polymers. SI‐ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) was performed from filter paper (FP) and high surface area nanopaper (NP).Larger amounts of polycaprolactone (PCL) were grafted from NP, compared to FP, owing to the higher amount of available initiating hydroxyl groups. Furthermore, the mechanical properties of PCL were improved by the grafting of FP and NP, as compared to pure PCL.It is challenging to characterize a polymer grafted from a surface. Hence, quartz crystal microbalance with dissipation (QCM‐D) was employed to investigate SI‐ROP in real time from a cellulose model surface. Furthermore, it was shown by colloidal probe AFM that increased lengthof grafted PCL, from cellulose microspheres, improved the interfacialadhesion to a pure PCL surface, suggesting that chain entanglements havea significant impact on the interfacial properties. Increased temperatureand time in contact also improved the adhesion.In order to investigate the degree of substitution (DS) and the degree of polymerization (DP), PCL‐grafted hydrolyzed cellulose cotton linters (HCCL) were studied by solid state NMR. It was found that despite a DS of only a few percent, the surface character changed considerably; furthermore, the DS was virtually independent of the DP. To increase theamount of grafted polymer, ring‐opening metathesis polymerization (ROMP) of norbornene was performed from FP. Short polymerizationtimes and low temperatures resulted in highly grafted surfaces. Alternatively, physical adsorption by electrostatic interactions was employed to modify a cellulose model surface in the QCM‐D. Cationic latex nanoparticles of poly(dimetylaminoethyl methacrylate‐co‐methacrylicacid)‐block‐poly(methyl methacrylate) were produced by reversible addition‐fragmentation chain‐transfer (RAFT)‐mediated surfactant‐freeemulsion polymerization by polymerization‐induced self‐assembly (PISA).This strategy does not require any organic solvents and could potentiallybe introduced in industrial processes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 77 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014-2
Keyword
Surface modification, cellulose, covalent modification, physical adsorption, polymer synthesis
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-140859 (URN)978-91-7501-987-1 (ISBN)
Public defence
2014-02-21, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, KFCE 8508Formas
Note

QC 20140203

Available from: 2014-02-03 Created: 2014-02-03 Last updated: 2014-02-03Bibliographically approved
2. Surface Modification of Nanocellulose towards Composite Applications
Open this publication in new window or tab >>Surface Modification of Nanocellulose towards Composite Applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanocelluloses have attracted great interest during recent decades owing to their renewability, abundancy and remarkable physical and mechanical properties. The aim of this work was to investigate new strategies for surface modification and functionalization of nanocelluloses and their subsequent incorporation in polymer-host matrices.

Nanocomposites of cellulose nanofibrils (CNF) and polycaprolactone (PCL) were produced by employing CNF nanopaper (NP) as a template and surface-initiated ring-opening polymerization (SI-ROP) of ε-caprolactone (ε-CL). SI-ROP of ε-CL from filter paper (FP) was also carried out for comparison. A larger amount of PCL was grafted from NP than from FP. The grafted NP had stronger mechanical properties than neat PCL.

Cellulose nanocrystal (CNC)-reinforced polyvinyl acetate (PVAc) nanocomposites were also investigated. CNC were modified via “SI-reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthate” (SI-RAFT/MADIX) polymerization of vinyl acetate (VAc). The resulting nanocomposites exhibited improved mechanical performance than the unmodified CNC.

It is generally agreed that covalent grafting is superior to physical adsorption for the modification of a reinforcing agent. However, this hypothesis has never been thoroughly investigated. CNC was modified either through covalent grafting or through physical adsorption of poly(butyl methacrylate) (PBMA). Both methods resulted in improved mechanical performance than that of pure PCL or PCL containing unmodified CNC. However, covalent grafting gave the best mechanical performance even at high relative humidity.

Functionalized CNC (F-CNC) were obtained through a versatile methodology employing organic acids bearing a functional group were employed for the simultaneous acid hydrolysis and esterification of cellulose fibers. This provided a facile route for the preparation of F-CNC.

Abstract [sv]

Intresset för nanocellulosa har ökat markant under de senaste decennierna eftersom de är förnyelsebara, finns att tillgå i stor mängd, och har mycket bra fysikaliska och mekaniska egenskaper. Syftet med detta arbete var att undersöka nya strategier för ytmodifiering och funktionalisering av nanocellulosa och dess inkorporering i polymera matriser.

Nanokompositer av cellulosa nanofibriller (CNF) och polykaprolakton (PCL) framställdes genom att CNF nanopapper (NP) användes som ett startmaterial från vilken ε-kaprolakton (ε‑CL) polymeriserades med ringöppningspolymerisation (SI-ROP). Som jämförelse ympades även ε-CL från filterpapper (FP) med SI-ROP. Resultatet var att större mängd av polykaprolakton (PCL) ympades från NP jämfört med FP. Det ytmodiferade NP hade bättre mekaniska egenskaper jämfört med ren PCL.

Nanokompositer av cellulosananokristaller (CNC) och polyvinylacetat (PVAc) undersöktes också. CNC modifierades via “SI-reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthate” (SI-RAFT/MADIX) polymerisation av vinylacetat (VAc). Nanokompositerna uppvisade bättre mekaniska egenskaper jämfört med omodifierade CNC.

Man har antagit att kovalent ympning är en överlägsen metod för modifiering av ett förstärkande element jämfört med fysikalisk adsorption, men denna hypotes har aldrig undersökts ordentligt. CNC har modifierats endera genom kovalent ympning eller fysikalisk adsorption av poly(butylmetakrylat) (PBMA). Båda metoderna gav förbättrad mekanisk prestanda jämfört med ren PCL och PCL innehållande omodifierad CNC, men kovalent ympning gav bäst prestanda även vid hög relativ fuktighet.

Funktionell CNC (F-CNC) framställdes genom en användbar metod som baseras på organiska syror med en funktionell grupp. F-CNC erhålls genom att hydrolysen av cellulosafibrer utförs genom att använda en kombination av sur hydrolys och förestring. Detta är en enkel och mycket användbar metod för att framställa F-CNC.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 1, 78 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:12
Keyword
Nanocellulose, surface modification, functionalization, composites
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-184091 (URN)978-91-7595-888-0 (ISBN)
Public defence
2016-04-22, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160324

Available from: 2016-03-24 Created: 2016-03-23 Last updated: 2017-02-15Bibliographically approved

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Boujemaoui, AssyaMalmström, EvaBerglund, LarsCarlmark, Anna

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