RAFT kinetics revisited: Revival of the RAFT debate

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Abstract

Recently, two electron spin resonance (ESR)-based methods for the determination of addition and fragmentation rate coefficients in dithiobenzoate-mediated reversible addition fragmentation transfer (RAFT) polymerization were introduced, one being based on a spin-trapping method and the other on single-laser pulse initiation in conjunction with ESR detection at microsecond time resolution. For the RAFT-intermediate radical fragmentation rate, coefficient data differing by six orders of magnitude were obtained, which cannot be explained by the usual model dependencies, that is the so-called cross-termination versus stable intermediate model. Even under consideration of fast cross-termination in both cases, the large difference persists. Both the experimental designs are thus critically reviewed to identify potential error sources and to explain the vast difference in the individual results. Both techniques appear to be robust and only small interferences could be identified. Finally, recommendations for the refinement of the individual techniques are given to achieve a consistent kinetic picture of the underpinning reaction equilibria.

Original languageEnglish
Pages (from-to)4154-4163
Number of pages10
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume49
Issue number19
DOIs
Publication statusPublished - 1 Oct 2011
Externally publishedYes

Keywords

  • ESR/EPR
  • kinetics (polym)
  • reversible addition fragmentation chain transfer (RAFT)
  • spin trapping

Cite this

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title = "RAFT kinetics revisited: Revival of the RAFT debate",
abstract = "Recently, two electron spin resonance (ESR)-based methods for the determination of addition and fragmentation rate coefficients in dithiobenzoate-mediated reversible addition fragmentation transfer (RAFT) polymerization were introduced, one being based on a spin-trapping method and the other on single-laser pulse initiation in conjunction with ESR detection at microsecond time resolution. For the RAFT-intermediate radical fragmentation rate, coefficient data differing by six orders of magnitude were obtained, which cannot be explained by the usual model dependencies, that is the so-called cross-termination versus stable intermediate model. Even under consideration of fast cross-termination in both cases, the large difference persists. Both the experimental designs are thus critically reviewed to identify potential error sources and to explain the vast difference in the individual results. Both techniques appear to be robust and only small interferences could be identified. Finally, recommendations for the refinement of the individual techniques are given to achieve a consistent kinetic picture of the underpinning reaction equilibria.",
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RAFT kinetics revisited : Revival of the RAFT debate. / Junkers, Thomas.

In: Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 49, No. 19, 01.10.2011, p. 4154-4163.

Research output: Contribution to journalArticleResearchpeer-review

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AU - Junkers, Thomas

PY - 2011/10/1

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N2 - Recently, two electron spin resonance (ESR)-based methods for the determination of addition and fragmentation rate coefficients in dithiobenzoate-mediated reversible addition fragmentation transfer (RAFT) polymerization were introduced, one being based on a spin-trapping method and the other on single-laser pulse initiation in conjunction with ESR detection at microsecond time resolution. For the RAFT-intermediate radical fragmentation rate, coefficient data differing by six orders of magnitude were obtained, which cannot be explained by the usual model dependencies, that is the so-called cross-termination versus stable intermediate model. Even under consideration of fast cross-termination in both cases, the large difference persists. Both the experimental designs are thus critically reviewed to identify potential error sources and to explain the vast difference in the individual results. Both techniques appear to be robust and only small interferences could be identified. Finally, recommendations for the refinement of the individual techniques are given to achieve a consistent kinetic picture of the underpinning reaction equilibria.

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