Highly 1,4-Selective Copolymerization of Ethylene and 1,3-Butadiene using Phenoxy–Imine–Ligated Titanium Complexes: Synthesis of Metathesis-Degradable Copolymers Containing Internal Olefins in the Main Chain for Telechelic Polyethylene

Abstract

A phenoxy-imine-ligated titanium (Ti) complex in combination with modified methylaluminoxane efficiently facilitated the selective 1,4-insertion of 1,3-butadiene (BD) during the copolymerization of ethylene and BD, achieving a selectivity of 85%. The resulting poly(ethylene-ran-BD), which contains internal olefins along the main chain, was subsequently degraded using a metathesis catalyst in the presence of ethylene, yielding telechelic polyethylene (PE) with terminal vinyl groups at both chain ends. Notably, this telechelic PE demonstrated superior thermal properties compared to the telechelic PE obtained from the copolymerization of ethylene and BD using (Me2Si(NtBu)CpMe4)TiMe2—a well-known constrained geometry complex—followed by metathesis degradation. The melting point of the telechelic PE was found to be influenced by the presence of cyclic moieties, which originated from intramolecular cyclization subsequent to the 1,2-insertion of BD, followed by the insertion of an ethylene monomer during copolymerization.