Redox-switchable α-diimine palladium catalysts for control of polyethylene topology. (28th September 2019)

• Record Type: Journal Article
• Authors: Mundil, Robert; Wilson, Lucy E.; Schaarschmidt, Dieter; Císařová, Ivana; Merna, Jan; Long, Nicholas J.
• Is Part Of: Polymer. Volume 179(2019)
• Publication Date: 2019-09-28
• Subjects: α-diimine palladium catalyst -- Living/controlled olefin polymerization -- Ferrocene; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2019.121619
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: A series of palladium complexes bearing ferrocene substituted α-diimine ligands was synthesized and investigated for ethene polymerization at different conditions to modulate the extent of "chain-walking" mechanism and regulate branching and topology of resulting polyethylenes. All ferrocene substituted complexes catalyzed living/controlled ethene polymerization. The ability of ferrocene substituted palladium complexes to provide polyethylenes with dendritic topology was proved by measuring their Mark-Houwink plots. In-situ chemical oxidation of ferrocene moieties via silver triflate was used to affect the catalyst electronic structure and support the "chain-walking" mechanism. Oxidation of palladium catalyst led to its destabilization while the catalytic activity of newly formed sites was substantially increased. It was demonstrated that catalyst oxidation is a powerful tool to regulate the topology of resulting polyethylenes. Graphical abstract: Image 1 Highlights: Newly synthesized Pd complexes with ferrocene substituted α-diimine ligands. All complexes provide living/controlled ethene polymerization. Chemical oxidation of Pd complexes gives more densely branched polyethylenes. Redox switch of Pd catalyst can regulate the PE topology.