Miscibility and Crystallization Behaviors of Poly(butylene succinate) and Poly(L-lactic acid) Segments in Their Multiblock Copoly(ester urethane)

Miscibility and crystallization behaviors of poly(butylenes succinate) (PBS) and poly(L-lactic acid) (PLLA) segments in their multiblock copoly(ester urethane) were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The single glass transition and depressed crystallization temperatures of PEUs with different compositions suggest that PBS and PLLA segments are miscible in amorphous phase of PEUs. Nonisothermal crystallization kinetics of PEUs was studied by Avrami and Mo methods; both results suggest that the crystallization rates of PEUs decreased with increasing weight fraction of PLLA segments. POM results indicate that banded spherulites were formed for PEUs when PLLA segments were introduced, and the band spacing increased with weight fraction of PLLA segments. The investigation of WAXD demonstrated the crystal structure of PEUs was the same as that of PBS, suggesting the crystallization of PEUs arose from PBS segments, and PLLA segments were unable to crystallize in PEUs.