Nickel‐Catalyzed Reductive Homodimerization of Brominated Polystyrene Chains

A nickel‐based catalytic system leading to high yields (≈80%) of polymer chain coupling has been developed. The extent of coupling (Xc) is found to be relatively high (>75%) and consistent across a wide range of catalyst loadings (0.1 – 1.0 equivalent with respect to the chain end), comparing fav...

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Bibliographic Details
Published in:Macromolecular chemistry and physics 2022-12, Vol.223 (24), p.n/a
Main Authors: Basler, Eleanor D., Chong, Jaden L., Heath, Chloe M., Ching, Katie S., Jennett, Shelby T., Tillman, Eric S.
Format: Article
Language:English
Subjects:
ATRP
Bromination
catalysis
Catalysts
Chains (polymeric)
Coupling
mechanisms
Nickel
Polymers
polystyrene
Polystyrene resins
reductive coupling
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Summary:A nickel‐based catalytic system leading to high yields (≈80%) of polymer chain coupling has been developed. The extent of coupling (Xc) is found to be relatively high (>75%) and consistent across a wide range of catalyst loadings (0.1 – 1.0 equivalent with respect to the chain end), comparing favorably with other chain‐end joining methods. A mechanistic cycle is proposed to occur with benzylic chain‐end radical intermediates, consistent with the addition of a nitroso radical trap substantially lowering coupling yields. The effect of the polymer chain end (Cl vs Br) and the halide associated with the nickel catalyst is also probed. Brominated polystyrene chains are effectively dimerized by a nickel‐catalyzed reductive coupling cycle, with high yields (80%) of chain‐end coupling observed across a wide range of conditions. The mechanism appears to involve the generation of polystyrene radicals which are captured by the nickel catalyst as part of catalytic cycle.
ISSN:1022-1352
1521-3935
DOI:10.1002/macp.202200320