Zwitterionic polymerization of lactide to cyclic poly(lactide) by using N-heterocyclic carbene organocatalysts

(Chemical Equation Presented) Closing the loop: The zwitterionic ring-opening polymerization of lactide in the presence of N-heterocyclic carbenes generates well-defined cyclic poly(lactide) (see scheme). The polymerization is rapid and produces macrocyclic polymers with high purity and exceptional control of molecular weight and polydispersity. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.