Synthesis and Deconstruction of Polyethylene-type Materials

Polyethylene deconstruction to reusable smaller molecules is hindered by the chemical inertness of its hydrocarbon chains. Pyrolysis and related approaches commonly require high temperatures, are energy-intensive, and yield mixtures of multiple classes of compounds. Selective cleavage reactions under mild conditions ( Collapse

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Grants

• H2020 European Research Council

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Affiliation(s)

Simon T. Schwab Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
Maximilian Baur Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
Taylor F. Nelson Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
Stefan Mecking Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany

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Rapid and Selective Photo-degradation of Polymers: Design of an Alternating Copolymer with an o-Nitrobenzyl Ether Pendant

The development of polymers with on-demand degradability is required to alleviate the current global issues on polymer-waste pollution. Therefore, we designed a vinyl ether monomer with an o-nitrobenzyl (oNBn) group as a photo-deprotectable pendant (oNBnVE) and synthesized an alternating copolymer with an oNBn-capped acetal backbone via cationic copolymerization with p-tolualdehyde (pMeBzA). The resultant alternating copolymer could be rapidly degraded into lower-molecular-weight compounds upon simple exposure to UV irradiation without any reactants or catalysts, while it was sufficiently stable toward heat and ambient light. This degradation proceeds via cleavage of the hemiacetal structure generated upon photo-deprotection of the oNBn pendant. The oNBn-peculiar degradability allowed the exclusive photo-degradation of the oNBnVE/pMeBzA segments in a diblock copolymer composed of oNBnVE/pMeBzA and benzyl vinyl ether (BnVE)/pMeBzA segments.

Synthesis and Degradation of Vinyl Polymers with Evenly Distributed Thioacetal Bonds in Main Chains: Cationic DT Copolymerization of Vinyl Ethers and Cyclic Thioacetals

We report a novel method to synthesize degradable poly(vinyl ether)s with cleavable thioacetal bonds periodically arranged in the main chains using controlled cationic copolymerization of vinyl ethers with a 7-membered cyclic thioacetal (7-CTA) via degenerative chain transfer (DT) to the internal thioacetal bonds. The thioacetal bonds, which are introduced into the main chain by cationic ring-opening copolymerization of 7-CTA with vinyl ethers, serve as in-chain dormant species to allow homogeneous propagation of vinyl ethers for all internal segments to afford copolymers with controlled overall and segmental molecular weights. The obtained polymers can be degraded into low- and controlled-molecular-weight polymers with narrow molecular weight distributions via hydrolysis. Various vinyl ethers with hydrophobic, hydrophilic, and functional pendants are available. Finally, one-pot synthesis of multiblock copolymers and their degradation into diblock copolymers are also achieved.

Cationic P,O-Coordinated Nickel(II) Catalysts for Carbonylative Polymerization of Ethylene: Unexpected Productivity via Subtle Electronic Variation

Transition-metal-catalyzed copolymerization of ethylene with carbon monoxide affords polyketones materials with excellent mechanical strength, photodegradability, surface and barrier properties. Unlike the widely used and rather expensive Pd catalysts, Ni-catalyzed carbonylative polymerization is very difficult since the strong binding affinity of CO to Ni deactivates the highly electrophilic metal center easily. In this study, various cationic P,O-coordinated Ni complexes were synthesized using the electronic modulation strategy, and the catalyst with strong electron-donating substituents exhibits an excellent productivity of 10⁴  g polymer (g Ni)^-1 , which represents a rare discovery that a Ni complex could operate with such exceptional efficiency in comparison with Pd catalysts. Notably, those Ni catalysts were also efficient for terpolymerization of ethylene, propylene with CO for producing commercial polyketone materials with low melting temperatures and easy processibility.