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Nickel catalysts build polyethylene-like materials that photodegrade

Copolymerizing ethylene and carbon monoxide creates polyethylene with ketone groups

by Bethany Halford
October 31, 2021 | A version of this story appeared in Volume 99, Issue 40

Phosphinophenolate-coordinated nickel complex.

Polyethylene is the world’s most common synthetic polymer, but its inert hydrocarbon chains prevent it from breaking down. This means it can linger in landfills forever. To make a less-persistent form of polyethylene, chemists at the University of Konstanz figured out a way to modify its long hydrocarbon chains with ketones at key spots (Science 2021, DOI: 10.1126/science.abi8183). The keto groups add reactive points to the hydrocarbon chain that makes the polymer degrade over the course of several months when it’s exposed to sunlight. Stefan Mecking and colleagues created the polymer by using phosphinophenolate-coordinated nickel complexes (example shown) to catalyze the copolymerization of ethylene and carbon monoxide. Previous attempts at this copolymerization with different catalysts have resulted in polymers with ketones on alternating carbons on the polymer chains, which significantly alters the polymer’s properties. Mecking’s group reports that after using conventional injection-molding techniques to process the new keto-modified polyethylene, the material’s tensile properties are similar to those of standard high-density polyethylene. The researchers note that further studies are needed to assess the material’s long-term performance, including its degradation mechanism and environmental impact..


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