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ARGET ATRP as a Tool for Cellulose Modification
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The importance of finding new applications for cellulose‐based products has increased, especially to meet the demand for new environmentally friendly materials, but also since the digitalization of our society will eventually decrease the need for paper. To expand the application area of cellulose, modification to improve and/or introduce new properties can be a requisite. Thus, the focus of this study has been to achieve fundamental knowledge about polymer grafting of cellulose via well‐controlled radical polymerization.

Cellulose, in the form of filter paper, has successfully been grafted via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) of the monomers: methyl methacrylate, styrene, and glycidyl methacrylate. The advantages of ARGET ATRP are that only a small amount of a copper catalyst is required and the reaction can be performed in limited amount of air; yet, providing for relatively well‐controlled reactions. These benefits can render ARGET ATRP an attractive method for industrial utilization.

The contact‐angle measurements of the grafted filter papers confirmed that the hydrophobicity of cellulose was significantly increased, even for shorter graft lengths. FT‐IR spectroscopy established that the amount of polymer successively increased with monomer conversion. High‐resolution FT‐IR microscopy (FT‐IRM) was proven to be a very useful technique for the analysis of cellulose substrates, displaying the spatial distribution of polymer content on cellulose fibers. The polymer was shown to be fairly homogenously distributed on the fiber.

An initiator with a reducible disulfide bond rendered cleavage of the polymer grafts possible, employing mild reaction conditions. The cleaved grafts and the free polymers – formed from a sacrificial initiator in parallel to the grafting – were shown to have similar molar masses and dispersities, confirming that the grafts can be tailored by utilizing a sacrificial initiator. Moreover, the initiator content on filter paper and microcrystalline cellulose was assessed.

A comparison between the two grafting techniques, grafting‐from cellulose via ARGET ATRP and grafting‐to cellulose via copper(I)‐catalyzed alkyne‐azide cycloaddition, was performed. To achieve a trustworthy comparison, the free polymer formed in parallel to the grafting‐from reaction was employed as the prepolymer in the grafting‐to approach, resulting in nearly identical graft length on the substrates for the two grafting methods. FT‐IRM analyses verified that under the selected conditions, the grafting‐from technique is superior to the grafting‐to approach with respect to controlling the distribution of the polymer content on the surface. The results were corroborated with X‐ray photoelectron spectroscopy.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 62 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:60
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-105762ISBN: 978-91-7501-544-6 (print)OAI: oai:DiVA.org:kth-105762DiVA: diva2:572014
Public defence
2012-12-14, K2, Teknikringen 28, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20121126

Available from: 2012-11-26 Created: 2012-11-26 Last updated: 2012-11-26Bibliographically approved
List of papers
1. ARGET ATRP for Versatile Grafting of Cellulose Using Various Monomers
Open this publication in new window or tab >>ARGET ATRP for Versatile Grafting of Cellulose Using Various Monomers
2009 (English)In: ACS Applied Materials & Interfaces, ISSN 1944-8244, Vol. 1, no 11, 2651-2659 p.Article in journal (Refereed) Published
Abstract [en]

In recent years, cellulose-based materials have attracted significant attention. To broaden the application areas for cellulose, polymers are often grafted to/from the surface to modify its properties. This study applies ARGET (activators regenerated by electron transfer) ATRP (atom transfer radical polymerization) when straightforwardly grafting methyl methacrylate (MMA), styrene (St), and glycidyl methacrylate (GMA) from cellulose in the form of conventional filter paper In the presence of a sacrificial initiator. The free polymer, formed from the free initiator in parallel to the grafting, was characterized by H-1 NMR and SEC, showing that sufficient control is achieved. However, the analyses also indicated that the propagation from the surface cannot be neglected compared to the propagation of the free polymer at higher targeted molecular weights, which is an assumption often made. The grafted filter papers were evaluated with FT-IR, suggesting that the amount of polymer on the surface increased with increasing monomer conversion, which the FE-SEM micrographs of the substrates also demonstrated. Water contact angle (CA) measurements implied that covering layers of PMMA and PS were formed on the cellulose substrate, making the surface hydrophobic, in spite of low DPs. The CA of the PGMA-grafted filter papers revealed that, by utilizing either aprotic or protic solvents when washing the substrates, it was possible to either preserve or hydrolyze the epoxy groups. Independent of the solvent used, all grafted filter papers were essentially colorless after the washing procedure because of the low amount of copper required when performing ARGET ATRP. Nevertheless, surface modification of cellulose via ARGET ATRP truly facilitates the manufacturing since no thorough freeze-thaw degassing procedures are required.

Keyword
ARGET ATRP, cellulose, controlled polymerization, grafting from, surface modification of cellulose, functional monomers, glycidyl, methacrylate, reducing agent, transfer radical polymerization, ring-opening polymerization, surface, modification, raft polymerization, reducing agent, methacrylate, polymers, fibers, nanoparticles, styrene
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-18979 (URN)10.1021/am900547g (DOI)000272039700032 ()2-s2.0-77951236507 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2012-11-26Bibliographically approved
2. Selective cleavage of polymer grafts from solid surfaces: assessment of initiator content and polymer characteristics
Open this publication in new window or tab >>Selective cleavage of polymer grafts from solid surfaces: assessment of initiator content and polymer characteristics
2011 (English)In: POLYM CHEM, ISSN 1759-9954, Vol. 2, no 3, 556-558 p.Article in journal (Refereed) Published
Abstract [en]

A novel initiator for atom transfer radical polymerization, also allowing for selective cleavage of polymer grafts, was designed and immobilized on a solid substrate. After cleavage, the initiator content was determined by utilizing Ellman's reagent and the cleaved polymer grafts were isolated and characterized by size exclusion chromatography.

Keyword
TRANSFER RADICAL POLYMERIZATION; CELLULOSE NANOCRYSTALS; RAFT POLYMERIZATION; ELECTRON-TRANSFER; POLYSTYRENE; NANOPARTICLES; CHEMISTRY; BRUSHES; STYRENE; FIBERS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-31852 (URN)10.1039/c0py00388c (DOI)000287378000009 ()2-s2.0-79951655921 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20110407Available from: 2011-04-07 Created: 2011-03-28 Last updated: 2012-11-26Bibliographically approved
3. Visualization of poly(methyl methacrylate) (PMMA) grafts on cellulose via high-resolution FT-IR microscopy imaging
Open this publication in new window or tab >>Visualization of poly(methyl methacrylate) (PMMA) grafts on cellulose via high-resolution FT-IR microscopy imaging
Show others...
2012 (English)In: Polymer Chemistry, ISSN 1759-9954, Vol. 3, no 2, 307-309 p.Article in journal (Refereed) Published
Abstract [en]

Cellulose surfaces grafted with PMMA of different graft lengths were characterized via high-resolution FT-IR microscopy imaging, visualizing the polymer distribution on the surface. The results from the FT-IR measurements can be compared with the molecular weights obtained from SEC and (1)H NMR of the macromolecules formed in solution.

Keyword
TRANSFER RADICAL POLYMERIZATION, SURFACES, NANOPARTICLES, FIBER
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-83789 (URN)10.1039/c1py00338k (DOI)000298991200006 ()2-s2.0-84855651837 (Scopus ID)
Note
QC 20120403Available from: 2012-04-03 Created: 2012-02-13 Last updated: 2012-11-26Bibliographically approved
4. Grafting Efficiency of Synthetic Polymers onto Biomaterials: A comparative study of grafting- from versus grafting- to
Open this publication in new window or tab >>Grafting Efficiency of Synthetic Polymers onto Biomaterials: A comparative study of grafting- from versus grafting- to
Show others...
2013 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, no 1, 64-74 p.Article in journal (Refereed) Published
Abstract [en]

In the present study, the two grafting techniques grafting-from - by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) - and grafting-to - by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) - were systematically compared, employing cellulose as a substrate. In order to obtain a meaningful comparison, it is crucial that the graft lengths of the polymers that are grafted from and to the substrates are essentially identical. Herein, this was achieved by utilizing the free polymer formed in parallel to the grafting-from reaction as the polymer for the grafting-to reaction. Four graft lengths were investigated, and the molar masses of the four free polymers (21 ≤ Mn ≤ 100 kDa; 1.07 ≤ M ≤ 1.26), i.e. the polymers subsequently employed in the grafting-to reaction, were shown to be in the same range as the molar masses of the polymers grafted from the surface (23 ≤ Mn ≤ 87 kDa; 1.08 ≤ M ≤ 1.31). The molecular weights of the chains grafted from the surface were established after cleavage from the cellulose substrates via size exclusion chromatography (SEC). High-resolution Fourier transform infrared microscopy (FT-IRM) was employed as an efficient tool to study the spatial distribution of the polymer content on the grafted substrates. In addition, the functionalized substrates were analyzed by X-ray photoelectron spectroscopy (XPS), contact angle (CA) measurements, and field-emission scanning electron microscopy (FE-SEM). For cellulose substrates modified via the grafting-from approach, the content of polymer on the surfaces increased with increasing graft length, confirming the possibility to tailor not only the length of the polymer grafts but also the polymeric content on the surface. In comparison, for the grafting-to reaction, the grafted content could not be controlled by varying the length of the preformed polymer: the polymer content was essentially the same for the four graft lengths. Consequently, the obtained results, when employing cellulose as a substrate and under these conditions, suggest that the grafting-from approach is superior to the grafting-to technique with respect to controlling the distribution of the polymeric content on the surface.

Keyword
Transfer Radical Polymerization, Modular Surface Modification, Initiated Arget Atrp, Raft Polymerization, Cellulose Fibers, Hydrophobic Modification, Responsive Cellulose, Click-Chemistry, Solid Cellulose, Cycloaddition
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-105760 (URN)10.1021/bm3013132 (DOI)000313605800008 ()2-s2.0-84872571250 (Scopus ID)
Note

QC 20130213

Available from: 2012-11-26 Created: 2012-11-26 Last updated: 2017-12-07Bibliographically approved

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