Novel mechanism for the formation of long-chain branching in polyethylene

✍ Scribed by Mark K. Reinking; Gene Orf; Douglas McFaddin

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 164 KB
• Volume: 36
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19981130)36:16<2889::aid-pola7>3.0.co;2-p

✦ Synopsis

Polyethylene produced by a vanadium-based polymerization catalyst contains long-chain branching as determined by NMR and rheology, even though the polymer has very low levels of vinyl unsaturation. A new mechanism is proposed for the formation of the long-chain branching, which involves COH bond activation of the polyethylene backbone through a -bond metathesis reaction, followed by ethylene insertion at the new VOC bond. Consistent with the proposed COH bond activation mechanism, the polymerization catalyst was also found to insert ethylene into the COH bonds of alkanes such as heptane. A bridged metallocene catalyst was also found to activate COH bonds of alkanes suggesting this new mechanism may explain the formation of long-chain branching in some metallocene-produced polyethylene.