Synthesis and Characterization of Stereo Multiblock Poly(lactic acid)s with Different Block Lengths by Melt Polycondensation of Poly( L ‐lactic acid)/Poly( D ‐lactic acid) Blends

Stereo multiblock PLAs with different block lengths are synthesized by melt polycondensation of low‐molecular‐weight poly( L ‐lactic acid)/poly( D ‐lactic acid) blends with a wide variety of $\overline {M} _{{\rm w}} $ in the range of 1.1–5.2 × 10 3 g · mol –1 . The average block length (ν av ) of the stereo multiblock PLAs increases with increasing $\overline {M} _{{\rm w}} $ of the blend and with the reaction temperature, whereas $\overline {M} _{{\rm w}} $ and PDI of the stereo multiblock PLAs increases with increasing $\overline {M} _{{\rm w}} $ of the blend, the reaction time, and the temperature. Stereo multiblock PLAs with ν av  > 7 are crystallizable to form stereocomplex crystallites, and the crystallinity and melting temperature of the stereo multiblock PLAs increases with increasing ν av and $\overline {M} _{{\rm w}} $ of the stereo multiblock PLAs.