Burkhard Köhler

Chemical Technologies for Exploiting and Recycling Carbon Dioxide into the Value Chain

While experts in various fields discuss the potential of carbon capture and storage (CCS) technologies, the utilization of carbon dioxide as chemical feedstock is also attracting renewed and rapidly growing interest. These approaches do not compete; rather, they are complementary: CCS aims to capture and store huge quantities of carbon dioxide, while the chemical exploitation of carbon dioxide aims to generate value and develop better and more-efficient processes from a limited part of the waste stream. Provided that the overall carbon footprint for the carbon dioxide-based process chain is competitive with conventional chemical production and that the reaction with the carbon dioxide molecule is enabled by the use of appropriate catalysts, carbon dioxide can be a promising carbon source with practically unlimited availability for a range of industrially relevant products. In addition, it can be used as a versatile processing fluid based on its remarkable physicochemical properties.

Transparent Films from CO2-Based Polyunsaturated Poly(ether carbonate)s: A Novel Synthesis Strategy and Fast Curing

Abstract Transparent films were prepared by cross‐linking polyunsaturated poly(ether carbonate)s obtained by the multicomponent polymerization of CO2, propylene oxide, maleic anhydride, and allyl glycidyl ether. Poly(ether carbonate)s with ABXBA multiblock structures were obtained by sequential addition of mixtures of propylene oxide/maleic anhydride and propylene oxide/allyl glycidyl ether during the polymerization. The simultaneous addition of both monomer mixtures provided poly(ether carbonate)s with AXA triblock structures. Both types of polyunsaturated poly(ether carbonate)s are characterized by diverse functional groups, that is, terminal hydroxy groups, maleate moieties along the polymer backbone, and pendant allyl groups that allow for versatile polymer chemistry. The combination of double bonds substituted with electron‐acceptor and electron‐donor groups enables particularly facile UV‐ or redox‐initiated free‐radical curing. The resulting materials are transparent and highly interesting for coating applications.

Light-mediated curing of CO2-based unsaturated polyethercarbonates via thiol–ene click chemistry

Facile cross-linking of CO2-based unsaturated polyethercarbonates with polymercaptanes via thiol–ene click chemistry makes them highly interesting sustainable pre-polymers for material applications as elastomers and sealants. CO2-Based unsaturated polyethercarbonates, characterised by a glass transition temperature well below room temperature, were obtained by convenient one-pot synthesis. Terpolymerization of CO2 with propylene oxide and allylglycidylether provided the polyethercarbonates with a defined number of pendant unsaturated bonds along the backbone of the polymer chain. The time-dependent viscoelastic behaviour during cross-linking with pentaerythritol tetrakis(3-mercaptopropionate) revealed faster curing with increasing content of double bonds in the pre-polymer. In parallel, the higher cross-linking density provided access to more rigid elastic materials.