Single Catalyst with Dynamic Ligands Enabled Synthesis of Olefin Block Copolymers

Abstract

Olefin block copolymers (OBCs) are among the most advanced classes of polyolefins, produced in large quantities as part of the approximately 200 million tons of polyolefins produced annually. However, current OBCs manufacturing relies on a complex, costly, two-catalyst process that requires hazardous chain shuttling agents. A more efficient approach using a single catalyst for the synthesis of the OBCs is highly desirable but remains significantly challenging. Traditional olefin copolymerization catalysts typically grow a single polymer chain and are incapable of generating block structures as they fail to incorporate α-olefins with the necessary precision. To achieve block copolymerization, the catalyst must simultaneously accomplish two seemingly contradictory tasks, efficiently and inefficiently incorporating α-olefins into the polymer chain. Here, we introduce a new approach for synthesizing OBCs using a single catalyst. By coupling this catalyst with a regulating agent, we enabled a one-step synthesis of OBCs with tunable hard/soft block ratios and high melting temperatures (∼120 °C). This method offers significant advantages, featuring its operational simplicity, elimination of chain shuttling agents, separate comonomer addition, or adjustments in reaction conditions. Mechanistic studies suggest that alkyl chains act as temporary ligands, dynamically influencing the catalyst’s polymerization behavior. This dynamic process allows the catalyst to alternate between efficient and inefficient α-olefin incorporators, thereby facilitating the synthesis of OBCs.