Polymerization of lactide and related cyclic esters by discrete metal complexes

This perspective highlights recent research on the preparation of polyesters by the ring-opening polymerization of cyclic esters employing well-characterized metal complexes. Particular focus is placed on the preparation of polylactide because of environmental advantages: it is biodegradable and its feedstock, lactide, is a renewable resource. A recurring theme is the correlation of precatalyst structure, often by X-ray crystallography, with polymerization activity and selectivity. Through this systematic approach to the deconvolution of catalyst structure/reactivity relationships, improved mechanistic understanding has been attained and key design criteria required for the development of new catalysts that exert control over the molecular parameters of polyesters and related copolymers have been revealed.