Searching for Stars: Selective Desulfurization and Fluorescence Spectroscopy as New Tools in the Search for Cross Termination Side-products in RAFT Polymerization

Steven L. Brown; Dominik Konkolewicz; Angus Gray-Weale; William B. Motherwell; Sébastien Perrier

doi:10.1071/CH09242

RESEARCH FRONT

Searching for Stars: Selective Desulfurization and Fluorescence Spectroscopy as New Tools in the Search for Cross Termination Side-products in RAFT Polymerization

Steven L. Brown ^A , Dominik Konkolewicz ^B , Angus Gray-Weale ^C , William B. Motherwell ^D and Sébastien Perrier ^B ^E

+ Author Affiliations

- Author Affiliations

^A Department of Colour and Polymer Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.

^B Key Centre for Polymers and Colloids, School of Chemistry, NSW 2006, Australia.

^C School of Chemistry, Monash University, Vic. 3800, Australia.

^D Department of Chemistry, UCL, Christopher Ingold Laboratories, 20 Gordon Street, London, WC1H 0AJ, UK.

^E Corresponding author. Email: s.perrier@chem.usyd.edu.au

Australian Journal of Chemistry 62(11) 1533-1536 https://doi.org/10.1071/CH09242
Submitted: 25 April 2009 Accepted: 20 July 2009 Published: 20 November 2009

Abstract

We present a novel approach to the examination of the ‘controversial’ three-armed stars that are argued to exist in rate-retarded reversible addition–fragmentation chain transfer (RAFT) polymerizations by using a fluorescent carbazole-containing RAFT agent that exhibits classical signs of retardation, and provides a route to polymer-RAFT agent cross termination. We also pioneer the use of an existing desulfurization technique for the purification of polymers by removal of the coloured RAFT derived moiety, with the added benefit of potentially isolating and identifying the presence of cross termination side-products. Our findings suggest that the rate retardation is either due to the RAFT intermediate being sufficiently stable that it does not cross terminate, or that most of cross termination events occur between the intermediate and short radicals. Our findings are consistent with a model proposed earlier by this group for rate retardation in RAFT systems, which assumed a slow rate for long-chain cross termination, and a fast short chain cross termination rate.

Acknowledgement

The authors acknowledge funding from the EPSRC (S.L.B.), an ARC Australian Postdoctoral Fellowship (A.G.-W.) and an Australian Postgraduate Award (D.K.). The authors thank Dr Chris Gabbutt for his advice on the Raney nickel catalysis and Dr Philip Vana, Institute of Physical Chemistry, University of Göttingen, for the PREDICI simulations.

References

Searching for Stars: Selective Desulfurization and Fluorescence Spectroscopy as New Tools in the Search for Cross Termination Side-products in RAFT Polymerization

Abstract

Acknowledgement

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