Ethyl-Branched Polyketones with Tailored Composition and Molecular Weight via Carbonylative Polymerization of Ethylene with 1-Butene

Abstract

Polyketones are an important class of engineering thermoplastics produced via the carbonylative polymerization of olefins, featuring excellent mechanical strength, chemical resistance, and barrier properties. However, all commercially available polyketones exclusively employ propylene as the comonomer, and the methyl substitution restricts the chain structure and property tunability. Herein, we report an earth-abundant nickel-catalyzed carbonylative polymerization of ethylene and 1-butene, delivering an ethyl-branched polyketone family with tailored composition (1-butene/CO (C4), 1.9–8.8 mol %) and molecular weight (65–500 kg/mol). A C4 incorporation as low as 3.5 mol % suffices to reduce the melting temperature (T_m) to 228 °C, comparable to commercial polyketone grades, while maintaining a productivity of ∼20 kg polyketone (g Ni)^–1. Compared with propylene-derived methyl side groups, the ethyl substituent enables superior toughness, impact resistance, barrier performance, and enhanced hydrophobicity. At a comparable α-olefin/CO incorporation level of ∼5.5 mol %, the representative sample PK_5.5,118 exhibits a tensile toughness of 23.9 MJ m^–3, 27.1% higher than that of the commercial Hyosung M630 grade with comparable yield strength, and a water vapor transmission rate of only 11.4 g m^–2 day^–1, corresponding to a 31.5% reduction relative to the M630 benchmark. This work establishes an industrially viable pathway to 1-butene-based polyketones, with strong potential to expand the polyketone product landscape beyond the current propylene-based portfolio.