Synthesis of topologically controlled functional polyethylenes: combining C–H activation with copolymerization of ethylene and polar monomers using a scandium catalyst

Abstract

The precise control of copolymer topology in the copolymerization of ethylene with heteroatom-functionalized alkenes is of much interest and importance, but has remained a challenge to date. We herein report a rare-earth-catalyzed strategy that utilizes C–H activation of comonomers to precisely control the functionality and topology of ethylene-based copolymers. By employing polar styrene- and norbornene-based monomers bearing tunable C–H activation motifs (e.g., anisole or aniline derivatives), highly branched functionalized polyethylenes are obtained through effective intramolecular C–H/ethylene insertion during copolymerization, whereas polar propenyl and allyl anisole enable end-functionalized linear polyethylene via C–H-activated chain transfer polymerization. By contrast, the copolymerization of thioether analogues lacking C–H activity with ethylene yields strictly linear copolymers. Mechanistic and microstructural studies confirm that this approach provides unprecedented control over polymer architecture—including branching density, functional group placement, and chain ends—highlighting the unique ability of rare-earth catalysts to combine polar-monomer incorporation with topology control.