Synthesis of PLLA-MPEG Diblock Copolymers by Microwave‐Assisted Copolymerization of L‐Lactide and Methoxy Poly(ethylene glycol)

PLLA-MPEG diblock copolymers with a controlled number‐average molar mass ranging from 7 330 to 117 610 g · mol−1 and an L‐lactide conversion ranging from 65.1 to 97.3% were synthesized effectively in 20 min at 100 °C by MPEG‐initiated ROP of L‐lactide under microwave irradiation. Prolonged microwave irradiation time led to the degradation of the copolymers because the ROP reaction and the thermal degradation reaction occurred simultaneously at the later stage of the reaction process. The differential scanning calorimetric and thermogravimetric study indicated that higher melting temperatures and thermal stability were obtained for PLLA‐MPEG diblock copolymers with longer PLLA segments.