Tailor-made block copolymers of <scp>l</scp>-, <scp>d</scp>- and <i>rac</i>-lactides and ε-caprolactone <i>via</i> one-pot sequential ring opening polymerization by pyridylamidozinc(<scp>ii</scp>) catalysts

Three-coordinated Zn(ii) complexes bearing sterically encumbered bidentate monoanionic [<i>N</i>,<i>N</i> ^-] pyridylamido ligands efficiently catalyze the ring opening polymerization of lactide (LA) and ε-caprolactone (CL). Owing to the polymerization controlled nature and high rate, precise stereodiblock poly(LLA-<i>b</i>-DLA) with different block lengths can be easily produced by one-pot sequential monomer addition at room temperature in short reaction times. NMR, SEC and DSC analyses confirm the production of highly isotactic diblock copolymers which crystallize in the high melting stereocomplex phase. Stereo-triblock and tetrablock copolymers of l-LA, d-LA and <i>rac</i>-LA have been synthesized similarly. Finally, a diblock poly(CL-<i>b</i>-LA) has been easily obtained by sequential addition of ε-caprolactone and lactide under mild conditions.