Accessing Syndiotactic Alternating Poly(lactic- co -glycolic acid) via Dual Regio- and Stereocontrol

Poly(lactic-co-glycolic acid) (PLGA) has attracted broad clinical attention for its exceptional biodegradability and biocompatibility. It is well established that the regio- and stereoregularity of PLGA has been shown to exert a significant influence on the material properties of the resulting PLGA. In this contribution, we report the design and synthesis of a class of readily tunable salalen aluminum complexes for regio- and stereoselective ROP of rac-MG. Ligand modification on this salalen system allowed us to access highly alternating and syndiotactic PLGA (Preg up to 98%; Pr up to 0.95 at 40 °C). The outstanding dual regio- and syndioselectivity has been exploited as an effective strategy for constructing a highly alternating copolymer P(MG-alt-EG) (Palt = 0.96). These findings manifested the beneficial effects of salalen Al complexes on regio- and stereocontrolled polymerization and represented an inspiring example to guide future catalyst design efforts.