Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Polycaprolactone Nanocomposites Reinforced with Cellulose Nanocrystals Surface-Modified via Covalent Grafting or Physisorption: A Comparative Study
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.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
Show others and affiliations
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 40, p. 35305-35318Article in journal (Refereed) Published
Abstract [en]

In the present work, cellulose nanocrystals (CNCs) have been surface-modified either via covalent grafting or through physisorption of poly(n-butyl methacrylate) (PBMA) and employed as reinforcement in PCL. Covalent grafting was achieved by surface-initiated atom transfer radical polymerization (SI-ATRP). Two approaches were utilized for the physisorption: using either micelles of poly(dimethyl aminoethyl methacrylate)-block-poly(n-butyl methacrylate) (PDMAEMA-b-PBMA) or latex nanoparticles of poly(dimethyl aminoethyl methacrylate-co-methacrylic acid)-block-poly(n-butyl methacrylate) (P(DMAEMA-co-MAA)-b-PBMA). Block copolymers (PDMAEMA-b-PBMA)s were obtained by ATRP and subsequently micellized. Latex nanoparticles were produced via reversible addition-fragmentation chain-transfer (RAFT) mediated surfactant-free emulsion polymerization, employing polymer-induced self-assembly (PISA) for the particle formation. For a reliable comparison, the amounts of micelles/latex particles adsorbed and the amount of polymer grafted onto the CNCs were kept similar. Two different chain lengths of PBMA were targeted, below and above the critical molecular weight for chain entanglement of PBMA (M-n,M-c similar to 56 000 g mo1(-1)). Poly(epsilon-caprolactone) (PCL) nanocomposites reinforced with unmodified and modified CNCs in different weight percentages (0.5, 1, and 3 wt %) were prepared via melt extrusion. The resulting composites were evaluated by UV-vis, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and tensile testing. All materials resulted in higher transparency, greater thermal stability, and stronger mechanical properties than unfilled PCL and nanocomposites containing unmodified CNCs. The degradation temperature of PCL reinforced with grafted CNCs was higher than that of micelle-modified CNCs, and the latter was higher than that of latex-adsorbed CNCs with a long PBMA chain length. The results clearly indicate that covalent grafting is superior to physisorption with regard to thermal and mechanical properties of the final nanocomposite. This unique study is of great value for the future design of CNC-based nanocomposites with tailored properties.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017. Vol. 9, no 40, p. 35305-35318
Keywords [en]
cellulose nanocrystals (CNCs), covalent grafting physisorption, reversible-deactivation radical polymerization (RDRP), poly(epsilon-caprolactone) (PCL), nanocomposites
National Category
Other Chemistry Topics
Identifiers
URN: urn:nbn:se:kth:diva-217193DOI: 10.1021/acsami.7b09009ISI: 000413131500079PubMedID: 28895728Scopus ID: 2-s2.0-85031302620OAI: oai:DiVA.org:kth-217193DiVA, id: diva2:1154510
Funder
Swedish Foundation for Strategic Research , EM11-0022
Note

QC 20171102

Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2019-01-23Bibliographically approved
In thesis
1. Inorganic and organic polymer-grafted nanoparticles: their nanocomposites and characterization
Open this publication in new window or tab >>Inorganic and organic polymer-grafted nanoparticles: their nanocomposites and characterization
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanocomposites (NCs) have been widely studied in the past decades due to the promising properties that nanoparticles (NPs) offer to a polymer matrix, such as increased thermal stability and non-linear electrical resistivity. It has also been shown that the interphase between the two components is the key to achieving the desired improvements. In addition, polymer matrices are often hydrophobic while NPs are generally hydrophilic, leading to NP aggregation. To overcome these challenges, NPs can be surface-modified by adding specific molecules and polymers. In the present work, a range of organic and inorganic NPs have been surface-modified with polymers synthesized by atom transfer radical polymerization (ATRP) or surface-initiated ATRP (SI-ATRP).Cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) are highly crystalline NPs that can potentially increase the Young’s modulus of the NC. In this study, a matrix-free NC was prepared by physisorption of a block-copolymer containing a positively charged (quaternized poly(2-(dimethylamino)ethyl methacrylate), qPDMAEMA) and a thermo-responsive (poly di(ethylene glycol) methyl ether methacrylate, PDEGMA). The modified CNF exhibited a thermo-responsive, reversible behavior. CNCs were polymer-modified either via SI-ATRP or physisorbed with poly (butyl methacrylate) (PBMA) to improve the dispersion and interphase between them and a polycaprolactone (PCL) matrix during extrusion. The mechanical properties of the NCs containing CNC modified via SI-ATRP were superior to the reference and unmodified materials, even at a high relative humidity.Reduced graphene oxide (rGO) and aluminum oxide (Al2O3) are interesting for electrical and electronic applications. However, the matrices used for these applications, such as poly(ethylene-co-butyl acrylate) (EBA) and low density polyethylene (LDPE) are mainly hydrophobic, while the NPs are hydrophilic. rGO was modified via SI-ATRP using different chain lengths of PBMA and subsequently mixed with an EBA matrix. Al2O3 was modified with two lengths of poly(lauryl methacrylate) (PLMA), and added to LDPE prior to extrusion. Agglomeration and dispersion of the NCs were dependent on the lengths and miscibilities of the grafted polymers and the matrices. rGO-EBA NCs showed non-linear direct current (DC) resistivity upon modification, as the NP dispersion improved with increasing PBMA length. Al2O3-LDPE systems improved the mechanical properties of the NCs when low amounts of NPs (0.5 to 1 wt%) were added, while decreasing power dissipation on the material.Finally, PLMA-grafted NPs with high polymer quantities and two grafting densities in Al2O3 and silicon oxide (SiO2) nanoparticles were synthesized by de-attaching some of the silane groups from the surfaces, either by hydrolysis or by a mild tetrabutylammonium fluoride (TBAF) cleavage. These compounds were characterized and compared to the bulk PLMA, and were found to have very interesting thermal properties.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 71
Series
TRITA-CBH-FOU ; 2018:15
Keywords
Si-ATRP, ATRP, polyelectrolytes, rGO, aluminium oxide, silica, CNF, CNC, PCL, LDPE, EBA, nanocomposites, matrix-free, extrusion
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-226888 (URN)978-91-7729-752-9 (ISBN)
Public defence
2018-05-25, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180427

Available from: 2018-04-27 Created: 2018-04-26 Last updated: 2018-04-27Bibliographically approved
2. Tailored adhesion of PISA-latexes for cellulose modification and new materials
Open this publication in new window or tab >>Tailored adhesion of PISA-latexes for cellulose modification and new materials
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on applying modification chemistry to already known cellulosic substrates from wood (i.e. cellulose nanofibrils, CNFs, and cellulose nanocrystals, CNCs). The modification is needed to overcome the drawbacks with the nanocellulosics alone, such as sensitivity to water (hydrophilicity) and the brittle material properties (however great stiffness). The first aim is to incorporate nanocellulosics into hydrophobic degradable materials of poly(ε-caprolactone) (PCL), resulting in aggregation if not modified. The challenge is to reach high fraction of nanocellulosics, whilst maintaining the flexibility of PCL and improving the properties of the resulting nanocomposite with the corresponding stiffness of the nanocellulosics. The second aim is to increase toughness and strain-at-break for nanocomposite materials of CNF-networks, to increase the plastic deformation equivalent of fossil-based polymeric materials such as polypropylene (PP). Aiming to achieve these goals, the thesis also includes new synthetic strategies of tailored-made set of block copolymers as modifying components. The modifying components, were synthesised by surfactant-free emulsion polymerisation and polymerisation induced self-assembly (PISA), so called PISA-latexes.

Two types of cationic polyelectrolytes, (poly(2-dimethylaminoethy methacrylate) (PDMAEMA) and poly(N-[3-(dimethylamino)propyl] methacrylamide (PDMAPMA)), being the corona of the latex, were synthesised. Followed by chain-extension with different hydrophobic monomers such as methyl methacrylate and butyl methacrylate, making up the core polymer of the resulting PISA-latex. The cationic PISA-latexes show narrow size distributions and the glass transition (Tg) of the core polymer can be varied between -40 °C to 150 °C. The PISA-latexes show strong adhesion to silica and cellulose surfaces as assessed by quartz crystal microbalance (QCM-D). Results also indicate that latexes with Tg below room temperature, considered soft, behave different in the wet state than latexes with Tg above room temperature, considered rigid. The softer latexes form clusters (visualised by imaging with microscopy and atomic force measurements (AFM)) and undergo film formation in the wet state. The latter, shown by colloidal probe measurements using AFM resulting in very large work of adhesion and pull-off forces.

The PISA-latexes compatibilize CNCs and different CNFs with PCL as a matrix polymer, observed by a small increase in stiffness for the final nanocomposites, however not at a level expected by rule-of-mixtures. The promising wet feeding technique results in large increase in stiffness but maintain PCL’s flexibility, above 200% strain-at-break, which is rarely observed for CNF-reinforced nanocomposites. The, in this case, rigid latex facilitate the dispersion of CNFs in the matrix without aggregation, until finally coalescing after processing and possibly giving rise to improved adhesion between CNF and the latex in the matrix, indicated by rheology measurements. Lastly, new nanocomposite films consisting of 75wt% CNF and 25wt% of PISA-latexes were produced and evaluated. The results show that CNF and rigid 100 nm sized PISA-latex, with PMMA core, gives a very tough double network, with strain-at-break above 28%, stiffness of 3.5 GPa and a strength of 110 MPa. These are impressive properties compared to commonly used fossil-based plastic materials.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 128
Series
TRITA-CBH-FOU ; 2019:7
Keywords
PISA, latex, RAFT, Cellulose Nanofibrils, Cellulose Nanocrystals, Nanocomposites
National Category
Polymer Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-241463 (URN)978-91-7873-086-5 (ISBN)
Public defence
2019-02-22, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20190123

Available from: 2019-01-23 Created: 2019-01-22 Last updated: 2019-01-23Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textPubMedScopus

Authority records BETA

Carlmark, AnnaMalmström, Eva

Search in DiVA

By author/editor
Boujemaoui, AssyaSanchez, Carmen CoboEngström, JoakimBruce, CarlFogelström, LindaCarlmark, AnnaMalmström, Eva
By organisation
Coating TechnologyWallenberg Wood Science Center
In the same journal
ACS Applied Materials and Interfaces
Other Chemistry Topics

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 521 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf