Copolymerization of carbon dioxide and butadiene via a lactone intermediate

Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2 H -pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide. Radical polymerization of a metastable lactone intermediate — formed from carbon dioxide and butadiene using a palladium catalyst — produces a high-CO 2 -content (29 wt%) polymer. This approach circumvents the thermodynamic and kinetic barriers typically associated with direct copolymerization of carbon dioxide and olefins, and can also be applied to one-pot co- and terpolymerization of carbon dioxide and 1,3-butadienes.