Access to Polyethylene-Polyester Block Copolymers in Continuous Flow through Single-Step Chain-End-Functionalized Polyethylene

Polar polyolefin block copolymer synthesis in continuous flow faces significant challenges due to the nature of the monomers, which require selective polymerization methods for the polymer segments. In this study, we developed a continuous flow strategy by utilizing 2-hydroxyethyl acrylate (HEA) chelated diimine Pd^II complex to generate a single-chain-end-functionalized polyethylene (PE-HEA) containing a free OH functionality, which is then employed as a macroinitiator for a ring-opening polymerization (ROP) to form PE-<i>b</i>-polyester diblock copolymers. This approach combines two distinct living polymerization processes stepwise, in which a semitelechelic PE is synthesized in the first flow reactor through a single-step living coordination-insertion polymerization (CIP), followed by an ROP in another flow system. This technique avoids a multistep postpolymerization process and ensures the controlled preparation of chain-end-functionalized PE, maintaining a low dispersity (∼1.10) throughout a broad range of molecular weights of 5.50 to 38.94 kg/mol, as well as the controlled polymerization of poly-(δ-valerolactone) (PVL) with molecular weights of 1.8 to 7.44 kg/mol with a narrow dispersity of ∼1.06. With this strategy, a range of distinct polar-PE block copolymers (PE-<i>b</i>-PVL) were prepared, in which the PE-HEA functions as a macroinitiator, facilitating a living ROP, yielding block copolymers with extended PVL and polylactide (PLA) segments. This work showcases that a functionalized chelated diimine Pd^II complex simplifies the preparation of chain-end-functionalized PE, which then can directly be employed to promote chain extension through ROP, forming polar-PE block copolymers in the flow system.