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Grafting Efficiency of Synthetic Polymers onto Biomaterials: A comparative study of grafting- from versus grafting- to
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
KIT Institute for Applied Materials (IAM-ESS).
KIT Institut für Technische Chemie und Polymerchemie.
KIT Institut für Technische Chemie und Polymerchemie.
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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.

Place, publisher, year, edition, pages
2013. Vol. 14, no 1, 64-74 p.
Keyword [en]
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: urn:nbn:se:kth:diva-105760DOI: 10.1021/bm3013132ISI: 000313605800008Scopus ID: 2-s2.0-84872571250OAI: oai:DiVA.org:kth-105760DiVA: diva2:572002
Note

QC 20130213

Available from: 2012-11-26 Created: 2012-11-26 Last updated: 2017-12-07Bibliographically approved
In thesis
1. ARGET ATRP as a Tool for Cellulose Modification
Open this publication in new window or tab >>ARGET ATRP as a Tool for Cellulose Modification
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:nbn:se:kth:diva-105762 (URN)978-91-7501-544-6 (ISBN)
Public defence
2012-12-14, K2, Teknikringen 28, KTH, Stockholm, 10:00 (English)
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Supervisors
Note

QC 20121126

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

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Carlmark, AnnaMalmström, Eva

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