Chronological review of the catalytic progress of polylactic acid formation through ring opening polymerization

The disposal of a large amount of polymer waste is one of the major challenges of this century. Use of bio-degradable polymers obtained from sustainable sources presents a solution to this problem. Poly lactic acid (PLA), a bio-degradable polymer, can be synthesized from sustainable sources as corn, starch, sugarcane and chips. Ring opening polymerization (ROP) of Lactide (LA) monomer using metal/bimetallic catalyst (Sn, Zn or Al) is the preferred method for synthesis of PLA. However, the PLA synthesized using such catalysts may contain trace elements of the catalyst. These catalyst traces are known carcinogens and as such should be (ideally) eliminated from the process. Use of the organic catalyst instead of metallic catalysts, may be one of the prominent solutions. Organic catalysts require the higher energy of activation for the ROP reaction of LA. Such energy requirement can be achieved through the application of alternative energy during the reaction. Alternative energy sources such as LASER, Ultrasound and microwave are prominent options to implement and process the ROP of PLA. This paper is an effort to emphasize the chronological review and to establish the current state-of-the-art in the field of PLA research