A Highly Active Chiral Indium Catalyst for Living Lactide Polymerization

摘要

Poly (lactic acid) (PL A), produced by ring-opening polymerization (ROP) of lactide (LA), is a leading biodegradable and biocompatible polyester with wide-ranging applications. Several well-defined Lewis acid catalysts have been developed for this reaction; prominent among them are metal alkoxides based on aluminum, zinc, and rare-earth metals, as well as organocatalysts. Known systems have successfully addressed one or more important factors in the ROP of LA, such as activity and catalyst toxicity. Enantioselectivity, in particular, has garnered much attention, and catalysts with exquisite control over PLA tacticity have been reported. Two modes of selectivity have been explored, enantiomorphic site control and chain-end control. These modes are not independent of each other; chain-end control can play an important role in systems that exhibit site control.