Development of Group 3 Catalysts for Alternating Copolymerization of Ethylene and Styrene Derivatives

Abstract

Alternating copolymers have the clearest and most defined microstructures among manmade polymers, having been promising building blocks to access synthetic polymers able to mimic biomaterials. The most successful approaches employ donor–acceptor monomer couples, enantiomers with different substituents, as well as specially designed cyclic monomers containing various units through ionic and living radical polymerizations. Herein we report the catalytic behaviors of rare-earth metal-based catalyst systems toward the direct copolymerization of ethylene with a series of unmasked polar styrenes and nonpolar styrenes. For the copolymerization of ethylene with para-methoxystyrene, the pyridyl side-armed fluorenyl-supported yttrium catalyst was inert, while its scandium analogue displayed moderate activity to give a random copolymer; the half-sandwich fluorenyl scandium catalyst provided a gel product. In contrast, the methyl-substituted N-heterocyclic carbene (NHC) side-armed fluorenyl scandium catalyst showed t...