Recent development of alkali metal complex promoted iso-selective ring-opening polymerization of rac-Lactide

Polyesters especially polylactide (PLA) are one of the most important and extensively studied biodegradable polymers for their use in medicine, agriculture, packaging, and drug delivery. Importantly, these polymers can be formed by the ring-opening polymerization (ROP) of lactide by carefully designed metal complexes that can act as catalysts for such reactions have emerged as useful tools to achieve this goal. In recent years, alkali metal–based organometallic complexes have appeared as an alternative to transition metal and rare-earth metal catalysts for the ROP of rac-lactide (rac-LA) systems. This strategy is advantageous because it obviates the need for pregenerated toxic metal precursors. This review highlights the progress of alkali metal–based catalysis for the ROP of rac-LA that comes out with a critical assessment of the futuristic research, spotlights the major developments achieved in the past few years, and provides an overview of the challenges and opportunities.