In search of a viable route to high-melting olefinic block copolymers

This paper describes the coordinative chain transfer polymerization (CCTP) of 1-octene and 4-methyl-1-pentene using three selected catalysts. Special attention was devoted to the reversibility and the rate of the polymeryl group transfer between the catalyst and the zinc-based chain transfer agent (CTA) as this determines whether the system could be used to produce corresponding olefinic block copolymers (OBCs) based on higher α-olefins, 1-octene and 4-methyl-1-pentene. All the three tested catalysts undergo chain transfer to zinc during the polymerization of 1-octene and 4-methyl1-pentene. Depending on the catalyst and monomer used, chain transfer to zinc appears to be either reversible or irreversible and, in all cases, the chain transfer and chain growth rate constants are of the same order of magnitude. All catalysts suffer from concurrent β-H transfer processes, which can be attributed to the steric hindrance of the applied α-olefins. For one of the catalysts, β-H transfer after 2,1-misinsertion appeared to be the prevalent competing chain transfer process. Adding a small amount of ethylene clearly reactivated the dormant site formed after 2,1-misinsertion without terminating the growing polymer chain, which opens the route to the formation of higher α-olefinbased OBCs.