Valorization of a CO2-Derived Lactone by Acyclic Diene Metathesis Polymerization

The exploitation of carbon dioxide (CO2) as a feedstock for the chemical processes has been an evasive venture due to its thermodynamic stability. The synthesis of highly functionalized metastable delta-lactone (3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one) was reported in 1970s which is formed by the condensation of CO2 and 1,3-butadiene in the presence of palladium catalyst. Several attempts have been made to utilize the intermediate for the polymerization processes, however, only a few have been successful. Here, we report a novel mechanism of metathesis polymerization of the metastable monomer by the action of a transition metal carbene complex (Hoveyda Grubb's II generation catalyst) to yield a new class of materials. The reaction mechanism for the polymerization has been proposed and substantiated by nuclear magnetic spectroscopic analysis. The obtained polymeric species consist of a complex unit structure where the cyclic lactone groups are connected by the olefin groups in different combinations.