Stereosequence- and topology-controlled synthesis of cyclic polyesters.

Lanthanum catalysts enable the one-pot synthesis of high-molecular-weight cyclic stereoblock and gradient copolyesters with enhanced mechanical properties.

• Why it matters: Controlling stereosequence and topology simultaneously in cyclic polyesters has been a significant challenge, limiting the development of materials with optimized properties.
• What they did: The researchers used lanthanum catalysts to achieve isoselective ring-expansion polymerization of amino acid-derived O-carboxyanhydrides, producing cyclic poly(β-hydroxy acids) and gradient copolyesters with narrow molecular-weight distributions and high molecular weights.
• The result: The resulting cyclic copolymers exhibit improved fracture strength and toughness while maintaining excellent oxygen barrier performance, demonstrating a new strategy for designing superior polymer materials.