From Impossible to Possible: Atom‐Economic Polymerization of Low Strain Five‐Membered Carbonates

Abstract The direct ring‐opening polymerization (ROP) of propylene carbonate (PC) only affords oligomers with substantial unidentified by‐products, which hinders the efficient utilization of PC. Through detailed studies, for the first time, a careful mechanism involving the in situ release of propylene oxide (PO) from PC decarboxylation is proposed. Further, we report a novel strategy of copolymerization of PC/cyclic anhydrides via in situ capture of the formed intermediates. Results show that PC is successfully transformed into polyesters. Especially for the ring‐opening alternating copolymerization (ROAC) of PC/phthalic anhydride (PA), a variety of advantages are manifold: i) slow‐release of PO ensuring a perfectly alternating structure; ii) quantitative and fast transformation of PC; iii) visualization of polymerization process by a CO 2 pressure gauge. Of importance, through tandem polymerizations, PC is fully transformed into polyesters and polycarbonates concurrently, thus achieving PC utilization with a high atom‐economy.