Well-Defined Poly(Ester Amide)-Based Homo- and Block Copolymers by One-Pot Organocatalytic Anionic Ring-Opening Copolymerization of N-Sulfonyl Aziridines and Cyclic Anhydrides

Abstract

We report a new synthetic methodology for poly(ester amide)s by anionic ring-opening copolymerization of N-sulfonyl aziridines and cyclic anhydrides. Phosphazenes organocatalysts have been found to promote a highly-active, controlled, and selective alternating copolymerization in the absence of any competitive side reaction (zwitterionic mechanism and exchange transacylations). Mechanistic studies have shown first-order dependence of the copolymerization rate in N-sulfonyl aziridines and phosphazenes, and zero-order in cyclic anhydrides. This one-pot methodology leads not only to homopolymers but also to poly(ester amide)-based block copolymers. Two catalytic cycles involving ring-opening alternating copolymerization of N-sulfonyl aziridines with cyclic anhydrides and ring-opening polymerization of N-sulfonyl aziridines have been proposed to explain the one pot synthesis of poly(ester amide)-based homo- and block copolymers.