Ring opening polymerization of l-lactide by an electron-rich Schiff base zinc complex: An activity and kinetic study

Abstract

A zinc complex with the Schiff base [(CH 3) 2NCH 2CH 2N CHC 6H 3(OH)(OMe)], LH, derived from 2-dimethylaminoethylamine and o-vanillin [Zn 2L 2(OBn) 2], has been synthesized and its structure has been established by X-ray crystallography and NMR spectroscopy. This zinc complex efficiently initiated the ring-opening polymerization (ROP) of l-lactide ( l-LA), and the polymerization runs were well controlled, giving polylactide end-capped with benzyl ester and hydroxyl groups. The structure of the ancillary ligands showed some influence on the catalytic activity, the introduction of electron-rich methoxy at ortho-phenoxy substituent resulted in a decrease of the polymerization rate. In addition, we also have found that the overall rate expression is d[lactide]/ dt = k p[lactide] 1[Zn 2L 2(OBn) 2] 1 in the kinetic study with the ROP of l-LA.