Molecular Mobilities in Biodegradable Poly(DL-lactide)/Poly(ε-caprolactone) Blends

The miscibility of poly(DL-lactide) and poly(c-caprolactone) (PDLLA/PCL) blends in a wide composition range was studied by the thermally stimulated depolarization currents technique by following the local and segmental dielectric relaxations changes as the blend composition is varied. The PCL primary relaxation is slightly shifted to higher temperatures as the PDLLA content increases, thus demonstrating the existence of a rich PCL phase and partial miscibility with PDLLA. Wide-angle X-ray scattering showed that neat PDLLA was amorphous, as expected for a sample with 12 mol % D-lactide isomer; nevertheless, the presence of 3D order was detected in the PDLLA that was melt blended with PCL. Differential scanning calorimetry also evidenced chain interaction by the decrease in the melting and crystallization temperatures as well as in the PCL crystallization kinetics which becomes slower in the presence of increasing amounts of PDLLA.