Synthesis of Biodegradable ABA-Type Block Copolymers Based on Poly(L-lactide) via Ring Opening Polymerization

초록

The ABA-type block copolymers were synthesized using ring-opening polymerization (ROP), employing poly(L-lactide) (PLLA) as the rigid chain and either poly(δ-valerolactone) (PVL) or poly(?-caprolactone) (PCL) as the flexible middle block. The initiator for the ROP was modified to introduce hydroxyl groups on both sides. The initiator's structure was confirmed using FTIR and H-NMR. The ABA block copolymers demonstrated higher molecular weight for PCL (51,000 g mol-1) compared to PVL (33,000 g mol-1) with similar molecular weight distributions. Additionally, PCL chains facilitated the formation of more metastable state of PLLA crystals compared to PVL, evident from the DSC thermograms. Upon hydrolytic degradation, PVL and PCL showed weight losses of approximately 74% and 37%, respectively after 3 weeks. The presence of PVL or PCL improved the degradability, making them promising candidates for thermoplastic elastomers (TPEs).