Acrylonitrile-Butadiene Rubber (NBR) Prepared via Living/Controlled Radical Polymerization (RAFT)

Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, 76128 Karlsruhe, Germany.
Macromolecular Rapid Communications (Impact Factor: 4.94). 09/2010; 31(18):1616-21. DOI: 10.1002/marc.201000162
Source: PubMed


In the current work we present results on the controlled/living radical copolymerization of acrylonitrile (AN) and 1,3-butadiene (BD) via reversible addition fragmentation chain transfer (RAFT) polymerization techniques. For the first time, a solution polymerization process for the synthesis of nitrile butadiene rubber (NBR) via the use of dithioacetate and trithiocarbonate RAFT agents is described. It is demonstrated that the number average molar mass, $\overline M _{\rm n} $, of the NBR can be varied between a few thousand and 60 000 g · mol(-1) with polydispersities between 1.2 and 2.0 (depending on the monomer to polymer conversion). Excellent agreement between the experimentally observed and the theoretically expected molar masses is found. Detailed information on the structure of the synthesized polymers is obtained by variable analytical techniques such as infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry, and electrospray ionization-mass spectrometry (ESI-MS).

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    ABSTRACT: The synthesis of acrylonitrile-butadiene rubbers (NBRs) via trithiocarbonate-mediated reversible addition fragmentation chain transfer (RAFT) polymerization of acrylonitrile (ACN) and 1,3-butadiene (BD) in solution under azeotropic conditions (38/62) was investigated for a broad range of common solvents: N,N-dimethylacetamide (DMAc), chlorobenzene, 1,4-dioxane, tert-butanol, isobutyronitrile, toluene, trimethylacetonitrile, dimethyl carbonate, acetonitrile, methyl acetate, acetone, and tert-butyl methyl ether. The gravimetrically determined conversions for the free radical polymerizations of ACN/BD after 22 h at 100 °C were in the range of 15% for methyl acetate to 35% for DMAc. The origin of the differences in conversion is attributed to the unequal decomposition behavior of the employed azo initiator 2,2′-azobis(N-butyl-2-methylpropionamide) (1) in the solvents under investigation, as determined by ultraviolet–visible (UV–vis) spectroscopy. Relative decomposition of 1 in solution (0.1 mol L−1) at 100 °C was calculated from the UV–vis spectra for selected solvents. 90% of 1 in DMAc was decomposed after 22 h, 83% in tert-butanol, 57% in 1,4-dioxane, 53% in isobutyronitrile, 45% in chlorobenzene, and 21% in toluene. The evolution of molecular weight with conversion using the initiator 1 was in accordance with the theoretically expected values, regardless of the solvent studied. Moreover, the RAFT-mediated copolymerization of ACN/BD in DMAc with azo initiators 1, 1-[(1-cyano-1-methylethyl)azo]formamide (2) and 1,1′-azobis(cyclohexanecarbonitrile) (3) was investigated. A strong deviation from the linear evolution of molecular weight due to a fast decomposition of these initiators – congruent with high primary radical delivery rates – at the selected temperature was observed when using 2 and 3. The deviation was not observed when using 1. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
    No preview · Article · Jan 2012 · Journal of Polymer Science Part A Polymer Chemistry
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    ABSTRACT: Graphene oxide (GO)/nitrile rubber (NBR) nanocomposites with various contents of GO were prepared by a solution-mixing method,in this study. The GO sheets were exfoliated from natural fake graphite by an improved Hummers method and could be further dispersed homogeneously in NBR matrix. The thickness and size of the GO sheets were observed by atomic force microscopy and transmission electron microscopy. The tribological properties of the GO/NBR nanocomposites were evaluated on a ring-block MRH-3 wear tester under dry sliding and water-lubricated conditions. The worn surface morphologies of the GO/NBR nanocomposites were observed by a scanning electron microscopy. It was found that under dry sliding, both the friction coefficient (COF) and specific wear rate of the nanocomposites decreased dramatically at first, then increased with increasing GO contents, while under water-lubricated condition, both the COF and specific wear rate of the nanocomposites decreased with increasing GO contents. Finally, the friction and wear mechanisms of the GO/NBR nanocomposites were tentatively proposed.
    Full-text · Article · Jan 2012 · Journal of Materials Science
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    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). Polymer–polymer coupling afforded linear polymers with molecular weights ranging from 2500 g mol−1 to 97000 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 azide–alkyne cycloaddition was extended towards the side-chain modification of acrylonitrile–butadiene 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.
    No preview · Article · Mar 2012
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