Polyethylene is the world’s most abundantly manufactured synthetic polymer, combining facile processing and low-cost production with excellent mechanical properties. The latter is particularly pronounced for high-density polyethylene (HDPE) and arises from a crystalline ordering of stretched hydrocarbon chains devoid of branching. However, these hydrophobic and chemically inert hydrocarbon chains can lead to problematic persistence when the materials are released to the environment, as they are not susceptible to common degradation pathways. One approach to overcome the drawbacks of crystalline polyethylene materials can be the direct catalytic copolymerization of ethylene with carbon monoxide.<br/>Here we report an advanced process development for the efficient catalytic copolymerization of ethylene and carbon monoxide to polyethylene materials, which contain in-chain ketone functionalization. Key is the application of suitable phosphinophenolate-coordinated Ni(II) catalysts, combined with an appropriate polymerization process design. This efficiently enables the non-alternating copolymerization of ethylene and carbon monoxide to incorporate a low density of individual ketones directly into the hydrocarbon chain. The so obtained polymers are not compromised in material properties, when compared to commercial polyethylene and can be processed by conventional techniques like injection molding. Despite fully retaining the desired material properties of HDPE, the in-chain ketones can act as predetermined breaking points and photodegradability is imparted. These novel polymers show enhanced degradation when exposed to simulated sunlight, thus potentially reducing the environmental persistence compared to conventional polyethylene.

Direct catalytic copolymerization of ethylene and carbon monoxide to polyethylene materials with in-chain ketones

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