The reactivity of N-vinylcarbazole in RAFT polymerization: trithiocarbonates deliver optimal control for the synthesis of homopolymers and block copolymers
Abstract
The use of various RAFT agents (ZC(S)SR) including dithiobenzoates (Z = Ph), trithiocarbonates (Z = SR′), xanthates (Z = OR′), and conventional and switchable N-aryldithiocarbamates (Z = NR′Ar) in RAFT polymerization of N-vinylcarbazole (NVC) has been explored with a view to establishing which is most effective. Consistent with earlier work, we find that xanthates and N-aryldithiocarbamates give adequate control (dispersities < 1.3) while dithiobenzoates give marked retardation. However, contrary to popular belief, we find that the polymerization of NVC is best controlled with trithiocarbonate RAFT agents, which provide both good molecular weight control, very narrow dispersities (1.1), and high end-group fidelity. The results demonstrate that NVC has intermediate reactivity, i.e. between that of the traditional more activated (MAMs; styrene, acrylates) and less activated monomers (LAMs; vinyl acetate, N-vinylpyrrolidone). A further key to good control is the selection of RAFT agent R substituent to be both a good leaving group and a good initiating radical. The cyanomethyl group meets these criteria whereas phenylethyl is a poor initiating radical for NVC polymerization. A further demonstration of the intermediate reactivity of NVC and the derived propagating radical was the successful preparation of both poly(n-butyl acrylate)-block-poly(N-vinylcarbazole) and poly(N-vinylcarbazole)-block-poly(n- butyl acrylate) with a trithiocarbonate RAFT agent (the sequence of block synthesis is not important). Two-dimensional, liquid chromatography near critical conditions-gel permeation chromatography (LCCC-GPC) has been applied to demonstrate block purity. The corresponding styrene-based blocks can also be successfully synthesized, however, the reinitiation of NVC polymerization by the polystyryl radical proved to be a constraint on the purity of polystyrene-block-poly(N-vinylcarbazole). © 2013 The Royal Society of Chemistry.Citation
Keddie, D.J., Guerrero-Sanchez, C. and Moad, G. (2013) The reactivity of N-vinylcarbazole in RAFT polymerization: trithiocarbonates deliver optimal control for the synthesis of homopolymers and block copolymers. Polymer Chemistry, 4, pp. 3591-3601.Publisher
Royal Society of ChemistryJournal
Polymer ChemistryAdditional Links
https://pubs.rsc.org/en/content/articlelanding/2013/PY/c3py00487bType
Journal articleLanguage
enDescription
This is an accepted manuscript of an article published by Royal Society of Chemistry in Polymer Chemistry on 30/04/2012, available online: https://doi.org/10.1039/C3PY00487B The accepted version of the publication may differ from the final published version.ISSN
1759-9954EISSN
1759-9962Sponsors
The authors gratefully acknowledge the Capability Development Fund of CSIRO Materials Science and Engineering for financial support. D.J.K. acknowledges the Office of the Chief Executive of CSIRO for an OCE postdoctoral fellowship and the School of Science and Technology at the University of New England for a start-up grant.ae974a485f413a2113503eed53cd6c53
10.1039/c3py00487b
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