Oxa-Michael addition polymerization of acrylates catalyzed by N-heterocyclic carbenes

Abstract

N-heterocyclic carbenes (NHCs) catalyze the oxa-Michael addition polymerization of hydroxyl functionalized acrylate monomers. This polymerization smoothly proceeded at room temperature to produce poly(ester-ether)s, which include new polymers having alicyclic, alkene, and alkyne groups in the main chain. The post polymerization modification of the alkene-functionalized polymer using thiol–ene “click” chemistry is demonstrated. The structure of poly(2-hydroxyethyl acrylate) was analyzed in detail by NMR and ESI-MS analyses and methanolysis, thus allowing estimation of the frequency of the transesterification. The NHC catalyst was covalently linked to the C terminal of the polymer chain, indicating that the NHC acts as a Lewis base to generate the zwitterionic intermediate without directly activating the hydroxyl groups of the monomers.