Crystallization Process with Aggregation of Small Crystallites for Polytrimethylene Terephtharate*

Polymer crystallization mechanism has explained the crystal nucleation and growth mechanism, while the existence of density fluctuations during the initial stage of crystallization has been discussed. In order to clarify the density fluctuations, the isothermal crystallization from the melt state of poly(trimethylene terephthalate) (PTT) has been studied by wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). Large scattering intensity in the low-q region (I_L(q)) has been observed by SAXS during the early stage of crystallizations. I_L(q) increases with time, reaches a maximum, and decreases. The results revealed the crystallization mechanism in which the small crystallites cover the entire sample with the aggregation regions[1]. The conclusion quantitatively showed that I_L(q) is due to the correlations among the heterogeneous aggregation regions of the crystallites.
[1] T. Konishi et al., Phys. Rev. Materials 2, 105602 (2018).