A bifunctional urea catalyst enables controlled/living ring-opening polymerization: access to various polyesters

Abstract

The development of bifunctional catalysts for synergistic catalysis has emerged as a key strategy for achieving precise polymer synthesis, particularly for challenging ring-opening polymerizations (ROP). We introduce a series of bifunctional catalysts designed for the controlled/living ROP of L-lactide (LLA) and other cyclic monomers. By combining hydrogen-bond donor groups with bio-based Lewis base anions, these catalysts achieve synergistic activation of both monomers and initiators. The catalytic system demonstrates high efficiency, excellent selectivity, and precise control over molecular weight, leading to a narrow dispersity (Đ_M < 1.20) across varied monomer-to-initiator ratios. The versatility of these catalysts extends to the polymerization of other monomers such as trimethylene carbonate (TMC) and δ-valerolactone (VL), showing similarly controlled outcomes. Mechanistic investigations using NMR titration reveal that the activation of monomers and initiators through cooperative hydrogen bonding is a key factor driving the high performance. This study provides valuable insights into catalyst design for ROP, offering a promising pathway for sustainable and efficient polymer synthesis.