T. Konishi1, D. Tadokoro1, Y. Kawahara1, K. Fukao2 and Y. Miyamoto2
1Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan
2Department of Physics, Ritsumeikan University, Noji-Higashi 1-1-1, Kusatsu 525-8577, Japan
Polymer crystallization mechanism especially at large supercooling has not been fully understood yet. Kaji et al. found that the density fluctuations occur in the early stage of crystallization in poly(ethylene terephthalate).  Research on such a fluctuations have been done from both theoretical  and experimental  aspects. But an interpretation for the fluctuations has not been fully obtained. Recently the strong density fluctuations are reported in the early stage of glass-crystallization process for poly(trimethylene terephthalate) (PTT). In order to clarify the density fluctuations in PTT, we have studied the crystallization processes of PTT from the glass and the melt by small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD).
The density fluctuations of several hundred Å have been obtained in the SAXS results in the early stage of crystallization process both from the glass and the melt. The fluctuations appear simultaneously with the generation of the nodular crystals of several tens Å. From the results we conclude that the fluctuations is due to the nodular crystals heterogeneously aggregated in space.
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 W.T. Chuang et al., Macromolecules 44, 1140 (2011). (link)