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Polymers 2018, 10(11), 1228; https://doi.org/10.3390/polym10111228

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

1
Polymer Reaction Design Group, School of Chemistry, Monash University, 19 Rainforest Walk, Clayton, VIC 3800, Australia
2
Institute for Materials Research, Hasselt University, Martelarenlaan 42, 3500 Hasselt, Belgium
*
Author to whom correspondence should be addressed.
Received: 19 October 2018 / Revised: 1 November 2018 / Accepted: 1 November 2018 / Published: 6 November 2018
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Abstract

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. View Full-Text
Keywords: online monitoring; flow polymerizations; dithiobenzoate-mediated RAFT polymerization; mass spectrometry; cross-termination online monitoring; flow polymerizations; dithiobenzoate-mediated RAFT polymerization; mass spectrometry; cross-termination
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Haven, J.J.; Junkers, T. Mapping Dithiobenzoate-Mediated RAFT Polymerization Products via Online Microreactor/Mass Spectrometry Monitoring. Polymers 2018, 10, 1228.

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