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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/18129

Title: Direct Access to Dithiobenzoate RAFT Agent Fragmentation Rate Coefficients by ESR Spin-Trapping
Authors: RANIERI, Kayte
Delaittre, Guillaume
Barner-Kowollik, Christopher
Issue Date: 2014
Citation: MACROMOLECULAR RAPID COMMUNICATIONS, 35 (23), p. 2023-2028
Abstract: The beta-scission rate coefficient of tert-butyl radicals fragmenting off the intermediate resulting from their addition to tert-butyl dithiobenzoate-a reversible addition-fragmentation chain transfer (RAFT) agent-is estimated via the recently introduced electron spin resonance (ESR)-trapping methodology as a function of temperature. The newly introduced ESR-trapping methodology is critically evaluated and found to be reliable. At 20 degrees C, a fragmentation rate coefficient of close to 0.042 s(-1) is observed, whereas the activation parameters for the fragmentation reaction-determined for the first time-read E-A = 82 +/- 13.3 kJ mol(-1) and A = (1.4 +/- 0.25) x 10(13) s(-1). The ESR spin-trapping methodology thus efficiently probes the stability of the RAFT adduct radical under conditions relevant for the pre-equilibrium of the RAFT process. It particularly indicates that stable RAFT adduct radicals are indeed formed in early stages of the RAFT polymerization, at least when dithiobenzoates are employed as controlling agents as stipulated by the so-called slow fragmentation theory. By design of the methodology, the obtained fragmentation rate coefficients represent an upper limit. The ESR spin-trapping methodology is thus seen as a suitable tool for evaluating the fragmentation rate coefficients of a wide range of RAFT adduct radicals.
Notes: [Ranieri, Kayte; Junkers, Thomas] Hasselt Univ, Inst Mat Res IMO, Polymer React Design Grp, B-3590 Diepenbeek, Belgium. [Delaittre, Guillaume; Barner-Kowollik, Christopher] Karlsruhe Inst Technol, Inst Tech Chem & Polymerchem, D-76128 Karlsruhe, Germany. [Delaittre, Guillaume] Karlsruhe Inst Technol, Inst Toxicol & Genet, D-76344 Karlsruhe, Germany. [Barner-Kowollik, Christopher] Karlsruhe Inst Technol, Inst Biol Grenzflachen, D-76344 Eggenstein Leopoldshafen, Germany. [Junkers, Thomas] IMEC, Div IMOMEC, B-3590 Diepenbeek, Belgium.
URI: http://hdl.handle.net/1942/18129
DOI: 10.1002/marc.201400518
ISI #: 000345977300007
ISSN: 1022-1336
Category: A1
Type: Journal Contribution
Validation: ecoom, 2016
Appears in Collections: Research publications

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