Microstructural Characterization of Molecular Weight Fractions of Ethylene/1,7-Octadiene Copolymers Made with a Constrained Geometry Catalyst

✍ Scribed by Deborah M. Sarzotti; Abhishek Narayan; Philip M. Whitney; Leonardo C. Simon; João B. P. Soares

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 229 KB
• Volume: 290
• Category: Article
• ISSN: 1438-7492
• DOI: 10.1002/mame.200500064

✦ Synopsis

Abstract

Summary: Ethylene was copolymerized with 1,7‐octadiene (OD) using a methylaluminoxane (MAO) activated constrained geometry catalyst (dimethylsilyl(N‐tert‐butylamido)(tetramethylcyclopentadienyl)titanium dichloride; CGC‐Ti) at 140 °C in toluene. The polymerization activity increased with the addition of small amounts of OD, reached a maximum, and then decreased at higher OD concentrations. The vinyl‐bond content of the polymers increased with increasing diene in the feed. Increasing OD concentrations led to the production of long chain branched (LCB) polyethylene (PE). Both 1,3‐cycloheptane (CY~7~) and 1,5‐cyclononane (CY~9~) units were identified in the copolymers, with the dominant CY~9~ structure accounting for approximately 53% percent of all rings. Selected copolymers were fractionated by molecular weight using a solvent/non‐solvent technique to obtain their detailed microstructure. The relative amounts of CY~7~ and CY~9~ structures were not a function of molecular weight. The number of vinyl functionalities decreased with increasing molecular weight, while the number of branches increased, indicating the incorporation of macromonomers with pendant or terminal vinyl groups.

Molecular weight distributions of ethylene homopolymer and three fractions.

magnified imageMolecular weight distributions of ethylene homopolymer and three fractions.