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Remote Perfluoroalkyl Substituents are Key to Living Aqueous Ethylene Polymerization
Author(s) -
Schnitte Manuel,
Scholliers Janine S.,
Riedmiller Kai,
Mecking Stefan
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201913117
Subject(s) - substituent , branching (polymer chemistry) , polymerization , ethylene , trifluoromethyl , chemistry , catalysis , polyethylene , aqueous solution , polymer chemistry , polymer , copolymer , chain transfer , nickel , photochemistry , organic chemistry , alkyl , radical polymerization
In various nickel(II) salicylaldiminato ethylene polymerization catalysts, which are a versatile mechanistic probe for substituent effects, longer perfluoroalkyl groups exert a strong effect on catalytic activities and polymer microstructures compared to the trifluoromethyl group. This effect is accounted for by a reduced electron density on the active sites, and is also supported by electrochemical studies. Thus, β‐hydride elimination, the key step of chain transfer and branching pathways, is disfavored while chain‐growth rates are enhanced. This enhancement occurs to an extent that enables living polymerizations in aqueous systems to afford ultra‐high‐molecular‐weight polyethylene for various chelating salicylaldimine motifs. These findings are mechanistically instructive as well as practically useful for illustrating the potential of perfluoroalkyl groups in catalyst design.