Stereo block copolymers of L‐ and D‐lactides

Sequential diblock copolymers composed of L ‐ and D ‐lactic acid residues were synthesized through a living ring‐opening polymerization of L ‐ and D ‐lactide initiated by aluminium tris(2‐propanolate). The composition of the block copolymers was varied by changing the reaction conditions and monomer over initiator ratio and confirmed by 1 H NMR analysis, molecular weight determination and optical rotation measurements. Molecular weights ranged from 1,3 to 2,0 · 10 4 with 1,2 < M̄ w / M̄ n < 1,4. Stereocomplex formation in all block copolymers was determined using differential scanning calorimetry showing melting temperatures of about 205°C.