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Investigation of iron complexes in ATRP: Indications of different iron species in normal and reverse ATRP
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).ORCID iD: 0000-0003-0663-0751
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-8348-2273
2011 (English)In: Journal of Molecular Catalysis A: Chemical, ISSN 1381-1169, E-ISSN 1873-314X, Vol. 346, no 1-2, 20-28 p.Article in journal (Refereed) Published
Abstract [en]

In an attempt to correlate the ATRP kinetics and the redox properties of the mediator, eight iron complexes with nitrogen, phosphorous and carboxylic acid containing ligands were investigated by electrochemical measurements and by using them as mediators in normal and reverse ATRP of MMA in DMF. The redox properties of the iron complexes in DMF, measured by cyclic voltammetry, did not differ significantly, which was reflected in the ATRP kinetics as the apparent rate constants were practically the same with all the complexing ligands. The degree of control over the polymerization was, however, much improved in reverse ATRP as compared to normal ATRP. In this ATRP system, the ligand type is not crucial for the redox or polymerization properties. Several observations indicate that the iron species in the two systems were not the same, the Fe(III) species resulting from oxidation of Fe(II) in normal ATRP is different from the starting Fe(III) species in reverse ATRP.

Place, publisher, year, edition, pages
2011. Vol. 346, no 1-2, 20-28 p.
Keyword [en]
Atom transfer radical polymerization (ATRP), Electrochemistry, Iron catalyst, Kinetics
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-32102DOI: 10.1016/j.molcata.2011.06.001ISI: 000294694500003Scopus ID: 2-s2.0-80051585641OAI: oai:DiVA.org:kth-32102DiVA: diva2:408875
Funder
Swedish Research Council, 621-2005-6190
Note
QC 20110406. Updated from manuscript to article in journal.Available from: 2011-04-06 Created: 2011-04-06 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Understanding the mechanisms behind atom transfer radical polymerization: exploring the limit of control
Open this publication in new window or tab >>Understanding the mechanisms behind atom transfer radical polymerization: exploring the limit of control
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Atom transfer radical polymerization (ATRP) is one of the most commonly employed techniques for controlled radical polymerization. ATRP has great potential for the development of new materials due to the ability to control molecular weight and polymer architecture. To fully utilize the potential of ATRP as polymerization technique, the mechanism and the dynamics of the ATRP equilibrium must be well understood.

In this thesis, various aspects of the ATRP process are explored through both laboratory experiments and computer modeling. Solvent effects, the limit of control and the use of iron as the mediator have been investigated. It was shown for copper mediated ATRP that the redox properties of the mediator and the polymerization properties were significantly affected by the solvent. As expected, the apparent rate constant (kpapp) increased with increasing activity of the mediator, but an upper limit was reached, where after kpapp was practically independent of the mediator potential. The degree of control deteriorated as the limit was approached.

In the simulations, which were based on the thermodynamic properties of the ATRP equilibrium, the same trend of increasing kpapp with increasing mediator activity was seen and a maximum was also reached. The simulation results could be used to describe the limit of control. The maximum equilibrium constant for controlled ATRP was correlated to the propagation rate constant, which enables the design of controlled ATRP systems.

Using iron compounds instead of copper compounds as mediators in ATRP is attractive from environmental aspects. Two systems with iron were investigated. Firstly, iron/EDTA was investigated as mediator as its redox properties are within a suitable range for controlled ATRP. The polymerization of styrene was heterogeneous, where the rate limiting step is the adsorption of the dormant species to the mediator surface. The polymerizations were not controlled and it is possible that they had some cationic character.

In the second iron system, the intention was to investigate how different ligands affect the properties of an ATRP system with iron. Due to competitive coordination of the solvent, DMF, the redox and polymeri­zation properties were not significantly affected by the ligands. The differences between normal and reverse ATRP of MMA, such as the degree of control, were the result of different FeIII speciation in the two systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 64 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:021
Keyword
polymerization, controlled radical polymerization, atom transfer radical polymerization, kinetics, catalysis, electrochemistry
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-32104 (URN)978-91-7415-933-2 (ISBN)
Public defence
2011-04-29, Sal K2, Teknikringen 28, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2005-6190
Note
QC 20110406Available from: 2011-04-06 Created: 2011-04-06 Last updated: 2011-04-13Bibliographically approved

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Jonsson, MatsMalmström, Eva

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