How are radicals (re)generated in photochemical ATRP?
Identifieur interne : 002A00 ( Main/Exploration ); précédent : 002999; suivant : 002A01How are radicals (re)generated in photochemical ATRP?
Auteurs : Thomas G. Ribelli [États-Unis] ; Dominik Konkolewicz ; Stefan Bernhard ; Krzysztof MatyjaszewskiSource :
- Journal of the American Chemical Society [ 1520-5126 ] ; 2014.
Abstract
The polymerization mechanism of photochemically mediated Cu-based atom-transfer radical polymerization (ATRP) was investigated using both experimental and kinetic modeling techniques. There are several distinct pathways that can lead to photochemical (re)generation of Cu(I) activator species or formation of radicals. These (re)generation pathways include direct photochemical reduction of the Cu(II) complexes by excess free amine moieties and unimolecular reduction of the Cu(II) complex, similar to activators regenerated by electron-transfer (ARGET) ATRP processes. Another pathway is photochemical radical generation either directly from the alkyl halide, ligand, or via interaction of ligand with either monomer or with alkyl halides. These photochemical radical generation processes are similar to initiators for continuous activator regeneration (ICAR) ATRP processes. A series of model experiments, ATRP reactions, and kinetic simulations were performed to evaluate the contribution of these reactions to the photochemical ATRP process. The results of these studies indicate that the dominant radical (re)generation reaction is the photochemical reduction of Cu(II) complexes by free amines moieties (from amine containing ligands). The unimolecular reduction of the Cu(II) deactivator complex is not significant, however, there is some contribution from ICAR ATRP reactions involving the interaction of alkyl halides and ligand, ligand with monomer, and the photochemical cleavage of the alkyl halide. Therefore, the mechanism of photochemically mediated ATRP is consistent with a photochemical ARGET ATRP reaction dominating the radical (re)generation.
DOI: 10.1021/ja506379s
PubMed: 25178119
Affiliations:
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Ribelli</name><affiliation wicri:level="1"><nlm:affiliation>Department of Chemistry, Carnegie Mellon University , 4400 Fifth Ave, Pittsburgh, Pennsylvania 15213, United States.</nlm:affiliation><country xml:lang="fr">États-Unis</country><wicri:regionArea>Department of Chemistry, Carnegie Mellon University , 4400 Fifth Ave, Pittsburgh, Pennsylvania 15213</wicri:regionArea><wicri:noRegion>Pennsylvania 15213</wicri:noRegion></affiliation></author><author><name sortKey="Konkolewicz, Dominik" sort="Konkolewicz, Dominik" uniqKey="Konkolewicz D" first="Dominik" last="Konkolewicz">Dominik Konkolewicz</name></author><author><name sortKey="Bernhard, Stefan" sort="Bernhard, Stefan" uniqKey="Bernhard S" first="Stefan" last="Bernhard">Stefan Bernhard</name></author><author><name sortKey="Matyjaszewski, Krzysztof" sort="Matyjaszewski, Krzysztof" uniqKey="Matyjaszewski K" first="Krzysztof" last="Matyjaszewski">Krzysztof Matyjaszewski</name></author></analytic><series><title level="j">Journal of the American Chemical Society</title><idno type="eISSN">1520-5126</idno><imprint><date when="2014" type="published">2014</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">The polymerization mechanism of photochemically mediated Cu-based atom-transfer radical polymerization (ATRP) was investigated using both experimental and kinetic modeling techniques. There are several distinct pathways that can lead to photochemical (re)generation of Cu(I) activator species or formation of radicals. These (re)generation pathways include direct photochemical reduction of the Cu(II) complexes by excess free amine moieties and unimolecular reduction of the Cu(II) complex, similar to activators regenerated by electron-transfer (ARGET) ATRP processes. Another pathway is photochemical radical generation either directly from the alkyl halide, ligand, or via interaction of ligand with either monomer or with alkyl halides. These photochemical radical generation processes are similar to initiators for continuous activator regeneration (ICAR) ATRP processes. A series of model experiments, ATRP reactions, and kinetic simulations were performed to evaluate the contribution of these reactions to the photochemical ATRP process. The results of these studies indicate that the dominant radical (re)generation reaction is the photochemical reduction of Cu(II) complexes by free amines moieties (from amine containing ligands). The unimolecular reduction of the Cu(II) deactivator complex is not significant, however, there is some contribution from ICAR ATRP reactions involving the interaction of alkyl halides and ligand, ligand with monomer, and the photochemical cleavage of the alkyl halide. Therefore, the mechanism of photochemically mediated ATRP is consistent with a photochemical ARGET ATRP reaction dominating the radical (re)generation.</div></front></TEI><affiliations><list><country><li>États-Unis</li></country></list><tree><noCountry><name sortKey="Bernhard, Stefan" sort="Bernhard, Stefan" uniqKey="Bernhard S" first="Stefan" last="Bernhard">Stefan Bernhard</name><name sortKey="Konkolewicz, Dominik" sort="Konkolewicz, Dominik" uniqKey="Konkolewicz D" first="Dominik" last="Konkolewicz">Dominik Konkolewicz</name><name sortKey="Matyjaszewski, Krzysztof" sort="Matyjaszewski, Krzysztof" uniqKey="Matyjaszewski K" first="Krzysztof" last="Matyjaszewski">Krzysztof Matyjaszewski</name></noCountry><country name="États-Unis"><noRegion><name sortKey="Ribelli, Thomas G" sort="Ribelli, Thomas G" uniqKey="Ribelli T" first="Thomas G" last="Ribelli">Thomas G. Ribelli</name></noRegion></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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