Living/controlled olefin polymerization initiated by nickel diimine complexes: The effect of ligand ortho substituent bulkiness

✍ Scribed by Jan Merna; Zdeněk Hošt’álek; Jan Peleška; Jan Roda

• Book ID: 104088008
• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 489 KB
• Volume: 50
• Category: Article
• ISSN: 0032-3861
• DOI: 10.1016/j.polymer.2009.08.030

✦ Synopsis

Polymerization of hex-1-ene and propene initiated by several methylalumoxane-activated diimine complexes was critically investigated. Effect of bulkiness of ortho aryl diimine substituents on extent of transfer reactions was examined. All of the complexes allowed us to prepare poly(hex-1-ene) with a very narrow molar mass distribution, molar mass being controlled by stoichiometry in a broad range of reaction conditions. Poly(hex-1-ene)s with molar mass between 15 and 220 kg mol À1 and dispersity (M w /M n ) between 1.01 and 1.20 were prepared by varying the catalyst, temperature and monomer concentration. Livingness of hex-1-ene polymerization was demonstrated for the first time for nickel complex bearing ethyl ortho aryl substituents by reinitiation of chain growth upon addition of a new portion of monomer. Complexes with ortho methyl substituents did not allow complete reinitiation of chain growth and despite its good control over molar mass cannot be classified as a living polymerization catalyst. Chain branching can effectively be controlled by the choice of the ligand structure due to the chain-walking mechanism. Transfer reactions were more pronounced in propene polymerization. Polypropylene with narrow molar mass distribution could not be prepared using complexes with methyl substituents.