Stereoregular, alternating ethylene–norbornene copolymers from monocyclopentadienyl catalysts activated with non-coordinating discrete anions

Abstract

Cyclic olefins copolymerize efficiently with ethylene using metallocene catalysts to make rigid engineering polyolefins with high chemical homogeneity. Materials with a high chemical homogeneity have value because they show reduced light scattering resulting in excellent clarity. The ultimate chemical homogeneity in a two component copolymer occurs when an alternating sequence distribution is achieved. Low symmetry bis-metallocenes have been shown to make alternating, stereoregular cyclic olefin copolymers under the right process conditions. These copolymers are semicrystalline and have high melt temperatures. Herein we report two group 4 monocyclopentadienyl catalyst systems that yield semicrystalline ethylene/norbornene copolymers over a range of reactor conditions. The clear copolymers have glass transition temperatures over 110°C and melt temperatures over 240°C. Further characterization data is presented and a short discussion of a plausible polymerization mechanism is given.