2020同步年報

040 ACTIVITY REPORT 2020 becomes broader, which represents an increased L p and a weakened nanograin spatial correlation ( i.e ., structure factor). The SAXS profiles exhibit a power-law scattering profile I( q ) ~ q P with P = -3.2 before reaching 270 °C, indi- cating that the molten state has a fractal structure with a fractal dimension ca. 3. The evolution of the normalized relative crystallinity of α and β crystals upon heating; rep- resentative deconvoluted WAXS profiles are illustrated in Figs. 2(a)−2(c) . As revealed by WAXS profiles, the cold-crys- tallized sPS-5%3MS specimens all exhibited an α-dominant structure, whereas a higher T c results in sharper reflections, implying more perfectly ordered crystals formed at a higher T c . Upon heating, the intensity of the reflections progres- sively decreases and finally exhibits amorphous halo profiles after reaching ca. 266 °C. In this work, the SAXS and WAXS results consistently show that the polymorphic behavior of sPS-3MS and sPS-4MS depends on the crystallization condition, whereas the presence of comonomer (especially 4MS) units tends to suppress more strongly the formation of β crystals in melt crystallization; the level of suppression enhances with in- creasing comonomer content. Based on the experimentally constructed melting behavior, here the corresponding T m ° of the sPS α or β crystal with varied 3MS and 4MS content was determined; the Sanchez−Eby theory 2 was introduced to interpret these observations from the viewpoint of ther- modynamics. (Reported by Wei-Tsung Chuang) This report features the work of An-Chung Su and his collab- orators published in Macromolecules 53 , 3059 (2020). TLS 23A1 IASW – Small/Wide Angle X-ray Scattering • SAXS, WAXS • Materials Science, Chemistry, Condensed-matter Physics References 1. P. H. Chen, S. J. Lin, J. C Tsai, U. S. Jeng, A. C. Su, Macro- molecules 53 , 3059 (2020). 2. I. C. Sanchez, R. K. Eby, Macromolecules 8 , 638 (1975).