Harnessing Composition and Sequence in Carbonylative Polymerization of Olefin for Tailored Material Properties

Abstract

Commercial polyolefin plastics are indispensable to modern society; however, their chemical inertness renders them environmentally persistent, thereby contributing to severe plastic pollution and ecological challenges. Accordingly, the development of commercially viable degradable materials with performance comparable to or even superior to that of conventional polyolefins has received substantial interest. Polyketones represent a compelling alternative: they are synthesized from commercially available olefin feedstocks and low-cost carbon monoxide (CO) and exhibit excellent mechanical strength, high thermal stability, superior barrier properties, and inherent photodegradability arising from their regularly spaced in-chain carbonyls. Despite the industrialization of palladium-catalyzed carbonylative polymerization, this reaction remains largely undeveloped, constrained by the reliance on a precious palladium catalyst, the poisoning effect of CO on transition metals, and the kinetic preference for CO insertion, which results in limited polymer compositions and sequence structures.

This Account summarizes our systematic research progress in catalyst design, structural regulation, and material properties for carbonylative polymerization. Building on the fundamental mechanistic difference between olefin homopolymerization and olefin/CO copolymerization, we have custom-designed and developed three classes of [P,O]-type ligand platforms: diphosphazane monoxide (PNPO), phosphine-sulfonate (PSO), and bisphosphine monoxide (BPMO). Their applications in Earth-abundant nickel-catalyzed carbonylative polymerization of ethylene reveal that the electron-donating ability of the ligands, rather than steric hindrance, could alleviate CO poisoning to the metal center and exert a dominant effect on catalytic activity and polymer molecular weight. To address the limitation in polymer composition, we have realized the first nickel-catalyzed carbonylative copolymerization of ethylene and propylene. Further extension to diverse α-olefins and polar monomers has greatly expanded the accessible polymer compositions, enabling the resulting polyketones to evolve from conventional resins and fibers into ultrastrong hot-melt adhesives and elastomers. Modulation of electronic asymmetry in [P,O]-Pd catalyst systems has enabled chain sequence control through nonalternating copolymerization to overcome the kinetic preference for CO insertion, yielding precisely tunable carbonyl content and uniform distribution along the polymer backbone. This nonalternating copolymerization produces a unique multiblock architecture integrating short polar segments and extended nonpolar methylene sequences. Such a multiblock copolymer could act as a robust compatibilizer for polyethylene/nylon blends, converting inherently brittle materials into mechanically tough composites. The introduction of true phosphorus chirality afforded a series of P-chirogenic palladium catalysts, which exhibited unprecedented enantioselectivity and living character in carbonylative polymerization of various vinylarenes. This approach yields a range of functionalized polyketone products with isotacticity up to 99% and molecular weights reaching 289 kg mol^–1. Notably, enantiopure fluoro-containing polyketone films exhibited unexpected chiral recognition performance toward l- and d-amino acids. Collectively, we have achieved efficient late-transition-metal-catalyzed carbonylative polymerization of diverse olefins via electronic modulation. This work not only establishes a theoretical framework for catalyst design in this polymerization, but also substantially expands the application scope of polyketone materials, outlining a promising pathway for their future development.