ROP of lactides and cyclic esters.

What ROP does

In ring-opening polymerization the strain of a cyclic ester — lactide, ε-caprolactone, glycolide — is relieved as the ring opens and adds to a growing chain. The result is a polyester whose ester backbone can be hydrolysed, which is what makes materials such as poly(lactide) biodegradable where polyolefins are not.

The catalyst does more than start the reaction. It governs the rate, the molecular weight distribution, and — critically for material properties — the tacticity of the resulting polymer.

Our contribution

• Ligand-controlled tacticity. Transition-metal organometallics and simple metal salts as ROP catalysts, resolving the relationship between the pendant ancillary ligand on the metal center and the polymerization behavior.
• Metal-free initiators. Phosphorus(V) compounds as metal-free ROP catalysts for cyclic esters and lactide, removing metal residues from polyesters destined for biomedical use.
• Chiral systems. Proline- and TADDOL-derived ligands on Zn(II), Al(III) and Group 4 centers for stereocontrol in the ROP of rac-lactide.
• Wealth from waste. L/D-lactide prepared from bio-derived lactic acid recovered from food waste, feeding the same ROP chemistry from a waste stream.

This work is supported by dedicated funding, including an Anusandhan National Research Foundation program on Harnessing Privileged Chiral Ligands for High-Performance Sustainable Polymers.