Synthesis and properties of Poly(L-lactide)-Poly(ε-caprolactone) multiblock copolymers by the self-polycondensation of diblock macromonomers

Abstract

Poly(L-lactide) (PLLA)-poly(ε-caprolactone) (PCL) multiblock copolymers (MBCs) were synthesized by the self-polycondensation of PLLA-PCL diblock copolymers. We synthesized three types of MBCs with degrees of polymerization of the lactide-caprolactone segments of 12-15 (MBC1), 24-26 (MBC2) and 49-50 (MBC3) to investigate the effect of the segment length on the properties. The strict control over the terminal functional groups of the diblock copolymers resulted in the formation of high-molecular weight MBCs (M w =(2.4-4.9) × 10 5 g mol -1). Differential scanning calorimetry (DSC) measurements suggest the phase mixing of PLLA and PCL segments in amorphous region and that the MBCs contain PCL-rich regions, the extent of which is influenced by the segment length. The X-ray diffraction patterns of the MBCs contain diffraction peaks originating from lactide segment crystals. High moduli (95-43 MPa) and elongation at break (∼500%) were observed for all the MBC films. The MBCs hydrolyzed slowly in comparison with PLLA, and the hydrophilic porous films of MBC2 were obtained. To estimate their potential as adhesion barrier films, the hydrophilic porous MBC films were implanted onto the abdominal side walls of rats. The MBC films effectively prevented the adhesion at the target site, but intermediate adhesion was observed at the suture site where the MBC film was fixed.