Lactide Polymerization Catalysts
Moisture and air stable indium complexes with great selectivity
- High conversion rates
- Exceptional control of molecular weight
- Not sensitive to moisture
- Excellent performance rates even in air
Polymers traditionally have been derived from petroleum, and these degradation resilient plastics fill up waste disposal sites around the world. More sustainable green solutions are needed. One successful bioplastics is polylactic acid (PLA), a biodegradable and bioactive thermoplastic polymer derived from renewable resources (starch, sugarcane). Although nowadays PLA is widely used for (food) packaging as well as medical implants, the cost for PLA is comparatively higher than synthetic plastics.
Researchers at The University of British Columbia have developed a novel indium-based catalyst for the polymerization of lactic acid. In these indium complexes, the metal is bound to SALAN or SALEN ligands, and especially the SALAN complexes display a unique stability. Their synthesis is straightforward, and in 3 easy synthetic steps the catalyst can be obtained in high yields. Various polymerization experiments have demonstrated that these novel indium complexes possess great catalytic activity and control over molecular weight for the ring-opening polymerization of LA (rac and meso) to PLA (heterotactic and syndiotactic). Furthermore, these catalysts are highly moisture and air stable, therewith allowing convenient handling. For example, in air and wet toluene at only 80°C, high molecular PLA was produced over the course of 4 h with catalytic conversion rates >99%.