Fast and Controlled Ring-Opening Polymerization of Cyclic Esters by Alkoxides and Cyclic Amides

Ring-opening polymerization is a powerful method for the synthesis of biodegradable and biorenewable polyesters. In this contribution, we report that the combination of alkali alkoxides and commercially available cyclic amides catalyzes fast and controlled ring-opening polymerization of L-lactide. The constrained cis C=N bond in the imidate catalyst is critical for achieving high catalytic activity. By optimizing the basicity of the catalyst, a good balance between activity and control (M-w/M-n < 1.1) is realized. A high amide/initiator ratio is essential for producing narrow dispersities and inhibiting transesterification.