Organocatalyzed ring-opening polymerization of proline-based lactones for poly(amino ester)s and cationic polymers with antibacterial activity

Abstract

Poly(amino ester)s (PAEs) are widely employed in diverse applications, particularly biomedicine, owing to their tunable functionality via amine group modification and the inherent biodegradability and biocompatibility of their polyester chains. Herein, we reported (thio)urea/base-catalyzed ring-opening polymerization of proline-based lactones for well-defined poly(amino ester)s. A series of (thio)ureas and organic bases were synthesized and combined to form various binary organocatalysts to explore the structure-activity relationships. Monomer conversion up to 95 % was achieved within 5 min. Kinetics studies and chain extension experiments confirmed the living/controlled nature of ROP. Four well-defined PAEs with high molecular weights (3150–51,340 g mol⁻¹) and narrow dispersity (Đ < 1.29) were produced. The resultant PAEs showed high thermal stability (T_d,5% = 224–350 °C) and T_m (189–244 °C). Furthermore, seven cationic random or block copolymers were synthesized through ring-opening copolymerization, followed by deprotection reaction. The effect of copolymer composition on the self-assembly behavior was investigated by DLS and TEM. Cationic random copolymers with high hydrophobic content demonstrated strong antimicrobial activity against E. coli, while those with high hydrophilic content were more active against S. aureus. This work would provide valuable insights into poly(amino ester)s and cationic polymers with tailored antimicrobial activity.