Synthesis, structure, crystallization and confinement of isodimorphic PBS-ran-PCL copolyesters

Zusammenfassung

In this thesis, the preparation of PBS-ran-PCL biodegradable and biocompatible copolyesters by ring opening-melt polycondensation polymerization with three different molecular weight is presented. The copolymers have been characterized by proton and carbon nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM), scanning electron microscopy (SEM), Raman, FT-IR, GIWAXS and wide angle X-ray scattering (WAXS). The PBS-ran-PCL copolyesters were able to crystallize in the entire composition range and displayed a pseudo-eutectic region. Most copolymers away from the pseudo-eutectic region exhibited a single crystalline phase (PBS-rich or PCL-rich crystalline phase), while within the pseudo-eutectic region the copolymers were double crystalline. Obtained results demonstrated that the copolymers are isodimorphic. Isothermal crystallization kinetics showed that both nucleation density and spherulitic growth rate of the copolyesters are determined by the component that constitutes the majority phase and was a strong function of composition and supercooling. For the infiltrated random copolyesters, results revealed that the nucleation process changed from heterogeneous in bulk to surface or homogeneous nucleation in the nanopores.