Poly(butylene succinate-ran-butylene adipate) random copolymers (PBSA) were prepared by melt polycondensation in a wide composition range. Polarized light optical microscopy (PLOM) was employed to observe their superstructural morphology while their thermal and structural properties were studied by differential scanning calorimetry (DSC) and in situ synchrotron Xray diffraction at wide and small angles (WAXS and SAXS). The morphological study revealed negative spherulitic superstructures with (PBS-rich) and without (PBA-rich) ring band patterns depending on composition. The crystallization temperature, melting temperature, and related enthalpies display a pseudoeutectic behavior as a function of composition. WAXS studies demonstrated that these random copolymers are isodimorphic, as their unit cell parameters are composition dependent and switch from PBS-like unit cells to β-PBA-like unit cells around the pseudoeutectic point. For PBA-rich compositions, the inclusion of butylene succinate units in the copolymer selectively promotes the formation of the orthorhombic β-polymorph, instead of the commonly observed monoclinic α-structure. The pseudoeutectic point is located around the 50:50 and 40:60 compositions and is characterized by a remarkable rate-dependent cocrystallization. Parallel DSC, SAXS, and WAXS results for these intermediate compositions show that depending on the cooling rate employed, the materials can exhibit single-or double-crystalline character either upon cooling or during subsequent heating. The structure, morphology, and properties of these versatile random copolymers can be tailored by composition and thermal history.

The effect of soft segment molecular weight and chemical structure on the morphology and final properties of segmented thermoplastic polyurethanes containing various hard segment contents has been investigated from the viewpoint of the degree of microphase separation. Vegetable oil‐based polyesters and corn sugar‐based chain extender have been used as renewable resources. The synthesis has been carried out in bulk without catalyst using a two‐step polymerization process. Physicochemical, thermal and mechanical properties, and also morphology, have been studied using Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, atomic force microscopy, X‐ray diffraction and mechanical testing. Chemical structure and molecular weight of polyols strongly affect the properties of the synthesized segmented thermoplastic polyurethanes. An increase in soft segment molecular weight leads to an increase of the degree of soft segment crystallinity and microphase separation, thus giving enhanced mechanical properties and higher thermal stability. Copyright © 2012 Society of Chemical Industry

It is demonstrated that the melting behavior and the morphology of three segmented thermoplastic polyurethane elastomers (TPUs) can be tailored by applying self-nucleation (SN) procedures. The self-nucleating temperature ranges for each of the TPU have been first determined by differential scanning calorimetry (DSC), while their morphology was studied by polarized light optical microscopy (PLOM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). When the samples are cooled at slow to moderate rates after SN, the crystallization temperature of the TPUs increases by up to 45 °C, when the samples are ideally self-nucleated. This large reduction in supercooling increases the melting points of the samples by approximately 20 °C. At the same time, SAXS and AFM experiments demonstrate the growth of thicker lamellae under these slow to moderate cooling conditions as compared to untreated samples. When ideally self-nucleated samples are rapidly quenched (e.g., at rates of 100 °C min–1 or larger) from their self-nucleation temperature to room temperature, the effects of SN described above on the morphology and melting points of the samples disappear for the TPUs that do not crystallize fast enough.