Interplay of reversible chain transfer andcomonomer incorporation reactions in coordinationcopolymerization of ethylene/1–hexene

Coordinative chain transfer polymerization (CCTP) has opened a new path for the development of novelproducts like olefin block copolymers and chain-end functional polyolefins. However, conflicting resultsare frequently reported on the catalyst performance including activity and comonomer selectivity under CCTPconditions. Here we have selected two catalysts including rac-ethylenebis(1-η5-indenyl)zirconocene and bis(imino)pyridine iron, with drastically different comonomer affinities. The effect of diethyl zinc as the chain transfer agent(CTA) on their individual performances is evaluated at different 1–hexene concentrations, in copolymerization withethylene. Combined thermal fractionation and GPC results confirm that not all chains experience the reversibletransfer reaction. Nevertheless, the metallocene catalyst shows twice activity and about 30% lower comonomerincorporation in the presence of CTA. Conversely, the late transition metal catalyst demonstrates lower activityand remains comonomer irresponsive. It could be concluded that, in addition to establishing a reversible transferreaction, CTA affects the nature of active centers. This finding can help designing olefin copolymers with a moredefined chemical composition based on CCTP reaction. Polyolefins J (2020) 7: 1-11

Keywords:

Coordination polymerization , reversible chain transfer reaction , chemical composition , microstructure