N-Heterocyclic Carbenes for the Organocatalytic Ring-Opening Polymerization of ε-Caprolactone

We report the synthesis of poly(ε-caprolactone) utilizing N-heterocyclic carbene (NHC) organocatalysts. Sterically unencumbered NHCs were found to be highly effective for the living ring-opening polymerization of ε-caprolactone under mild conditions. The NHCs were able to produce poly(ε-caprolactone)s with controlled molecular weights, low polydispersities, and well-defined end groups derived from the alcohol initiator. Star-shaped poly(ε-caprolactone)s with three and four arms were prepared using NHC organocatalysts and characterized by 1H NMR and GPC.