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

A zinc complex with the Schiff base [(CH3)2NCH2CH2NCHC6H3(OH)(OMe)], LH, derived from 2-dimethylaminoethylamine and o-vanillin [Zn2L2(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 = kp[lactide]1[Zn2L2(OBn)2]1 in the kinetic study with the ROP of l-LA.

Graphical abstractA new electron-rich Schiff base [(CH3)2NCH2CH2NCHC6H3(OH)(OMe)] zinc complex [Zn2L2(OBn)2] has been prepared and characterized by X-ray crystallography and NMR spectroscopy. Experimental results show that this complex is an excellent initiator toward the controlled polymerization of l-lactide (l-LA) and its activity decrease by the introduction of electron-rich methoxy at ortho-phenoxy substituent to the ancillary ligand. In addition, we also report that the overall rate expression is d[lactide]/dt = kp[lactide]1[Zn2L2(OBn)2]1 in the kinetic study with the ring opening polymerization of l-LA.Figure optionsDownload full-size imageDownload high-quality image (92 K)Download as PowerPoint slideHighlights► This zinc complex efficiently initiated the controlled polymerization of l-lactide. ► The introduction of methoxy at ortho-phenoxy leads to a decrease polymerization rate. ► The overall rate expression is d[lactide]/dt = kp[lactide]1[Zn2L2(OBn)2]1.