Amino Acid Platform for Poly(amino ester)s: Controlled Ring-Opening Polymerization, Complete Recyclability, and...

Poly(amino ester) (PAE) is a class of polyesters featuring backbone tertiary amines and ester bonds, combining biodegradability with tunable functionality for diverse applications. However, developing a versatile platform for the ring-opening polymerization (ROP) of diverse monomers to build PAE libraries remains a significant challenge. Herein, we present a readily available and versatile platform for synthesizing diverse PAEs from amino acids. A series of azalactone monomers were synthesized in a simple two-step process from renewable amino acids and diverse epoxides, allowing monomers with tailored ring size, substituents, and steric bulk. The azalactone monomers underwent organocatalytic controlled ROP. We systematically investigated the effect of monomer structures, including N-substituents, lactone core substituents, stereoconfiguration and ring size, on ROP reactivity. All resulting PAEs could be depolymerized into their initial monomers in quantitative yield, exhibiting first-order kinetics. The depolymerization rate constants showed an inverse correlation with the corresponding polymerization rate constants. Thermodynamics, kinetics and recyclability studies revealed that changing the azalactone structure could regulate their ceiling temperature (-20 ∼ 37 °C, 1.0 mol L^-1), thus adjusting the polymerizability and depolymerizability. This work offers valuable insights into the design of azalactone monomer libraries, the synthesis of PAEs, and the structure-activity relationships governing polymerization and depolymerization behavior.