Mapping Dithiobenzoate-Mediated RAFT Polymerization Products via Online Microreactor/Mass Spectrometry Monitoring

2-cyano-2-propyl dithiobenzoates (CPDB)-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization was monitored by online flow microreactor/mass spectrometry. This enabled the reactions to be followed in a time-resolved manner, closely resolving product patterns in the reaction...

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Veröffentlicht in:Polymers Jg. 10; H. 11; S. 1228
Hauptverfasser: Haven, Joris J., Junkers, Tanja
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Switzerland MDPI AG 06.11.2018
MDPI
Schlagworte:
Addition polymerization
Benzoates
Chain transfer
Equilibrium
Free radicals
Mass spectrometry
Microreactors
Molecular weight
Monitoring
NMR
Nuclear magnetic resonance
Polymerization
Scientific imaging
Shift reaction
Software
Solvents
Spectroscopy
Belgium
dithiobenzoate-mediated RAFT polymerization
mass spectrometry
cross-termination
flow polymerizations
online monitoring
ISSN:2073-4360, 2073-4360
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Zusammenfassung:2-cyano-2-propyl dithiobenzoates (CPDB)-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization was monitored by online flow microreactor/mass spectrometry. This enabled the reactions to be followed in a time-resolved manner, closely resolving product patterns in the reaction mixtures at any point in time. RAFT polymerization was investigated for low RAFT to monomer ratios, enabling the monitoring of the early stages of a typical RAFT polymerization. The expected transition from pre- to the RAFT main equilibrium is observed. However, very high abundancies for cross-termination products were also identified, both in the pre- and main equilibrium stage. This is a somewhat surprising result as such products have always been expected, but to date have not been observed in the majority of studies. Product isolation and NMR analysis revealed that cross-termination occurs in the para position of the benzoate ring and becomes fully irreversible via re-aromatization of the ring in a H-shift reaction. The present data suggest a pronounced chain-length dependence of the cross-termination reaction, which would explain why the products are seen here, but not in other studies.
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ISSN:2073-4360
2073-4360
DOI:10.3390/polym10111228