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Heterogeneous iron(II)-chloride mediated radical polymerization of styrene
KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.ORCID-id: 0000-0003-0663-0751
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.ORCID-id: 0000-0002-8348-2273
2009 (engelsk)Inngår i: Journal of Molecular Catalysis A: Chemical, ISSN 1381-1169, E-ISSN 1873-314X, Vol. 306, nr 1-2, s. 69-76Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In an attempt to perform atom transfer radical polymerization (ATRP) with a more environmentally friendly mediator, polymerization of styrene in the presence of iron(II)-chloride and EDTA was explored from a mechanistic point of view. The presence of EDTA, which normally can form a complex with FeCl2, had no influence on the polymerization results as both the mediator and EDTA were insoluble in the polymerization medium. A mechanism is suggested for the heterogeneous polymerization of styrene mediated by iron (II)-chloride in p-xylene at 50 °C. Varying the mediator amount more than 10-fold revealed that the rate limiting step at low mediator amounts was the adsorption of the initiator or dormant polymer to the mediator surface, whereas at higher mediator amounts, the rate limiting step was instead the activation step in the ATRP equilibrium. The mechanism changed to free radical polymerization in solution at a certain conversion, resulting in lower apparent rate constant and an increased amount of transfer and termination reactions. Chain extension with MMA showed that a significant proportion of the polymer chain ends were active also at high conversions.

sted, utgiver, år, opplag, sider
2009. Vol. 306, nr 1-2, s. 69-76
Emneord [en]
Atom transfer radical polymerization (ATRP), Heterogeneous, Iron chloride, Kinetics, Polystyrene
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-18528DOI: 10.1016/j.molcata.2009.02.024ISI: 000267084900011Scopus ID: 2-s2.0-67349222833OAI: oai:DiVA.org:kth-18528DiVA, id: diva2:336575
Merknad
QC 20100525Tilgjengelig fra: 2010-08-05 Laget: 2010-08-05 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Inngår i avhandling
1. Understanding the mechanisms behind atom transfer radical polymerization: exploring the limit of control
Åpne denne publikasjonen i ny fane eller vindu >>Understanding the mechanisms behind atom transfer radical polymerization: exploring the limit of control
2011 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2011. s. 64
Serie
Trita-CHE-Report, ISSN 1654-1081 ; 2011:021
Emneord
polymerization, controlled radical polymerization, atom transfer radical polymerization, kinetics, catalysis, electrochemistry
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-32104 (URN)978-91-7415-933-2 (ISBN)
Disputas
2011-04-29, Sal K2, Teknikringen 28, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Forskningsfinansiär
Swedish Research Council, 621-2005-6190
Merknad
QC 20110406Tilgjengelig fra: 2011-04-06 Laget: 2011-04-06 Sist oppdatert: 2011-04-13bibliografisk kontrollert

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