Accessing Functionalized Ultra-High Molecular Weight Poly(α-olefin)s via Hafnium-Mediated Highly Isospecific Copolymerization.

Abstract

Inspired by the favorable impact of heteroatom-containing groups in phenoxy-imine titanium and late transition metal catalysts, we design and synthesize a series of novel pyridylamido hafnium catalysts bearing -OMe (Cat-OMe), -CF3 (Cat-CF3), and -C6F5 (Cat-C6F5) substituents. Together with the established hafnium catalysts Cat-H and Cat-iPr by Dow/Symyx, these catalysts are applied in the polymerization of α-olefins, including 1-hexene, 1-octene, and 4M1P, as well as in the copolymerization of these α-olefins with a specifically designed polar monomer. The enhancement of polymer molecular weight derived from catalyst modification and the incorporation of polar monomers is discussed in detail. Notably, the new catalysts are all highly active for α-olefins polymerization, with catalyst Cat-CF3 producing isotactic polymers with the highest molecular weight (Mw = 1,649kg mol-1); in copolymerization with polar monomers, catalyst Cat-OMe yields isotactic copolymer with the highest molecular weight (Mw = 2,990kg mol-1). Interestingly, catalyst Cat-C6F5 bearing a -C6F5 group in the N-aryl moiety gives rise to poly(α-olefin) with reduced stereoselectivity. The findings of this study underscore the potential of heteroatom-containing groups in the development of early transition metal catalysts and the synthesis of polymer with novel structures. This article is protected by copyright. All rights reserved.