Polymerization of cyclic esters using N-heterocyclic carbene carboxylate catalysts

The ring-opening polymerization of β-butyrolactone and lactide in solvent-free conditions and using NHC carboxylates as a (pre)catalyst is described. This class of catalysts enables the synthesis of aliphatic polyesters. These organocatalysts, which are easily synthesized, are remarkably robust, thus allowing the use of a bench-top reaction setup. In addition, NHC carboxylates are highly active in bulk conditions without the use of additives. Also, we have demonstrated for the first time that decarboxylation of NHC carboxylates depends on the nature of solvents under polymerization conditions.