Effects of α-form or β-form nuclei on polymorphic crystalline morphology of poly(butylene adipate)

The effects of a-form and β-form nuclei on polymorphic morphology of poly (butylene adipate) (PBA)upon recrystallization from the molten state up to various T_max values were examined by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarized light microscopy (PLM). In this study, PBA with complex melting and polymorphism behaviour was used as a model for examining different types and extents of residual nuclei. As the PBA initially containing the sole α-crystal was brought to a molten state of various T_max, the extents of trace α-form crystal nuclei varied and were dependent on T_max. Furthermore, it did not matter whether, initially, the PBA α-or β-form crystals (or both) because only a single type of α-nuclei could be left upon treatment to the molten liquid state at T_max. Therefore, only the α-crystal in PBA had 'memory capacity' in the molten liquid state while the β-crystal did not. This was so because the latter had been completely transformed into the solid state prior to being heated into a liquid. PBA crystallized before α-nuclei could pack into α-crystal regardless of the crystallization temperature (T_c). For recrystallization from molten PBA without any nuclei, the crystalline polymorphism was correspondingly influenced by T_c.