Initiators for the stereoselective ring-opening polymerization of meso-lactide

Poly(lactides) (PLAs), or poly(lactic acid)s, are among the first commercial biodegradable polymers that have the potential to become commodity plastics. meso-Lactide, a by-product of L-lactide production, will become more easily available. Highly stereoregular poly(meso-lactides) should be crystalline and thus interesting as polymeric material. In this short review, initiators capable of inducing the stereoselective ring-opening polymerization of meso-lactide to ideally give syndiotactic or heterotactic PLAs will be discussed. Mechanistic discussions with regard to understanding the reactivity differences between the various lactide monomers are included.