Stereoselective Ring-Opening Polymerization of Racemic Ethylglycolide: Precisely Regulated Polyester Properties via Stereomicrostructure Control

Abstract

The development of high-performance, renewable polyesters with tunable mechanical properties is critical for advancing sustainable materials to replace petroleum-based plastics. Herein, a conceptually simple but highly effective strategy was employed for the stereoselective ring-opening polymerization (ROP) of racemic ethylglycolide (rac-EtG), affording polyesters with diverse sequence structures and a record-high isotacticity (P_m up to 0.99) among ROP of glycolide-type monomers. Strikingly, a simple adjustment of the steric hindrance at the 3-position of the salicylaldehyde moiety enabled a tunable switch in the stereoselectivity exhibited by the catalyst from atactic to isotactic and further to heterotactic. By tuning the stereomicrostructure of the polymer, a remarkable transition in ductility from 2.8% to 2119% was achieved. Typically, isotactic-riched poly(ethylglycolide) (ir-PEtG) exhibited an elongation at break of 569.9 ± 36.5% while maintaining a tensile strength of 26.7 ± 0.9 MPa. Furthermore, we demonstrated that a balanced distribution of crystalline and amorphous domains in the polymer microstructure enables simultaneous tuning of both strength and toughness.