Muhammad Afzal Subhani

Carbon dioxide (CO2) as sustainable feedstock for polyurethane production

A dream comes true: tailor-made polyethercarbonate polyols are synthesised from propylene oxide and CO2. Molecular weight and functionality of these polyethercarbonate polyols are controlled by the use of an appropriate alcohol starter enabling innovative applications as a polymer building block. Interestingly, the properties of the polyethercarbonate polyols can be adjusted in a wide range by tuning CO2 content and architecture. The feasibility of using such tailored polyethercarbonate polyols in the production of polyurethanes is demonstrated as a prime example for a novel CO2 utilization with industrial potential.

Highly active Cr(III) catalysts for the reaction of CO2 with epoxides

This paper describes the synthesis and characterization of [Cr(babhq)OAcF(EtOH)] (OAcF− = CF3CO2−) as well as the application of the complex as the catalyst in the reaction of CO2 with epoxides. While cyclic propylene-carbonate was obtained as the sole product when propylene oxide was used as epoxide, alternating polycarbonate was obtained with cyclohexene oxide. Following the course of the reaction with in situ IR spectroscopy revealed that a direct pathway to the formation of cyclic carbonate prevails in the case of propylene oxide whereas the polycarbonate obtained from cyclohexene oxide is prone to degradation to cyclic carbonate. The differences in chemoselectivity are rationalised on the basis of the propensity of the ligand to adopt a podand-like structural motif allowing for an inner-sphere mechanism.

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.

Anion effect controlling the selectivity in the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide

Summary The choice of the anion has a surprisingly strong effect on the incorporation of CO2 into the polymer obtained during the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide. The product span ranges from polyethercarbonates, where short polyether sequences alternate with carbonate linkages, to polycarbonates with a strictly alternating sequence of the repeating units. Herein, we report on the influence of the coordination ability of the anion on the selectivity and kinetics of the copolymerisation reaction.

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.