N-heterocyclic carbenes as organocatalysts in controlled/living ring-opening polymerization of O-carboxyanhydrides derived from l -lactic acid and l -mandelic acid

An organocatalytic approach to controlled/living ring-opening polymerizations (ROPs) of O-carboxyanhydrides (OCAs) using N-heterocyclic carbenes (NHCs) as nucleophilic catalysts has been investigated. NHCs with different structures were used in order to compare the catalytic performances in the ROP of OCA of l-lactic acid. ¹H NMR, SEC, and MALDI-TOF MS measurements of the products clearly indicated a controlled/living manner of the polymerization. The controlled/living nature was further confirmed by kinetic and chain extension experiments. Additionally, polylol initiators were used to produce α,ω-dihydroxy telechelic, 3-, and 4-armed star-shaped polymers. Moreover, star-shaped diblock copolymer, bearing methyl and phenyl side groups, has been successfully synthesized with OCA/NHC system.