Synthesis of star-shaped poly(ε-caprolactone)-b-poly(L-lactide) copolymers: From star architectures to crystalline morphologies

摘要

Hexa-armed star-shaped poly(e-caprolactone)-block-poly(L-lactide) (6sPCL-b-PLLA) with dipentaerythritol core were synthesized by a two-step ring-opening polymerization. GPC and 1H NMR data demonstrate that the polymerization courses are under control. The molecular weight of 6sPCLs and 6sPCL-b-PLLAs increases with increasing molar ratio of monomer to initiator, and the molecular weight distribution is in the range of 1.03-1.10. The investigation of the melting and crystallization demonstrated that the values of crystallization temperature (T_c), melting temperature (T _m), and the degree of crystallinity (X_c) of PLLA blocks are increased with the chain length increase of PLLA in the 6sPCL-b-PLLA copolymers. On the contrary, the crystallization of PCL blocks dominates when the chain length of PLLA is too short. According to the results of polarized optical micrographs, both the spherulitic growth rate (G) and the spherulitic morphology are affected by the macromolecular architecture and the length of the block chains.