Issue 4, 2012

High molecular weight acrylonitrile–butadiene architectures via a combination of RAFT polymerization and orthogonal copper mediated azide–alkyne cycloaddition

Abstract

α-Functional nitrile butadiene rubber (NBR) building blocks were employed in the copper mediated 1,3-dipolar Huisgen coupling upon addition of 1,4-bis(azidomethyl)benzene (4). Polymerpolymer coupling afforded linear polymers with molecular weights ranging from 2500 g mol−1 to 97 000 g mol−1 and polydispersities from 1.1 to 1.6. The α-functional NBR building blocks were obtained via the reversible addition–fragmentation chain transfer (RAFT) copolymerization of acrylonitrile (AN) and 1,3-butadiene (BD) at 100 °C, utilizing the high temperature azo initiator 1,1′-azobis(cyclohexane-1-carbonitrile) and chlorobenzene or acetone as solvents. A novel alkyne-functional trithiocarbonate 2 was synthesized in 64% yield via the N,N′-dicyclohexylcarbodiimide mediated coupling of 2-((dodecylsulfanyl)carbono-thioyl)sulfanyl propanoic acid (DoPAT, 1) and propargyl alcohol. 2 was shown to be an efficient controlling agent for the controlled/living radical copolymerization of acrylonitrile and 1,3-butadiene. The use of copper mediated azidealkyne cycloaddition was extended towards the side-chain modification of acrylonitrilebutadiene rubbers as well as applied in the synthesis of branched and cross-linked NBR structures. For this purpose an acrylonitrile-1,3-butadiene–propargyl methacrylate (PMA) terpolymer of 3900 g mol−1 with a PDI of 1.3 was synthesized by a DoPAT-mediated RAFT polymerization. Herein, monomers were employed in the ratio of 56 : 35 : 9 (BD : AN : PMA). The ability of the terpolymer to undergo side-chain modification was demonstrated upon addition of 1-undecane azide. Cross-links were established via addition of 1,4-bis(azidomethyl)benzene. The current study provides the first successful approach to employ an orthogonal conjugation technique on this technically important class of synthetic rubbers.

Graphical abstract: High molecular weight acrylonitrile–butadiene architectures via a combination of RAFT polymerization and orthogonal copper mediated azide–alkyne cycloaddition

Supplementary files

Article information

Article type
Paper
Submitted
15 Nov 2011
Accepted
08 Jan 2012
First published
07 Feb 2012

Polym. Chem., 2012,3, 1048-1060

High molecular weight acrylonitrilebutadiene architectures via a combination of RAFT polymerization and orthogonal copper mediated azidealkyne cycloaddition

C. J. Dürr, S. G. J. Emmerling, P. Lederhose, A. Kaiser, S. Brandau, M. Klimpel and C. Barner-Kowollik, Polym. Chem., 2012, 3, 1048 DOI: 10.1039/C2PY00547F

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