Block–Stereoblock Copolymers of Poly(ϵ‐Caprolactone) and Poly(Lactic Acid)

: A magnesium complex of the type {ONNN}Mg-HMDS wherein {ONNN} is a sequential tetradentate monoanionic ligand is introduced. In the presence of an alcohol initiator this complex catalyzes the living and immortal homopolymerization of the lactide enantiomers and ϵ-caprolactone at room-temperature with exceptionally high activities, as well as the precise block copolymerization of these monomers in a one-pot synthesis by sequential monomer addition. Copolymers of unprecedented microstructures such as the PCL-b-PLLA-b-PDLA and PDLA-b-PLLA-b-PCL-b-PLLA-b-PDLA block-stereoblock microstructures that feature unique thermal properties are readily accessed.