Temperature-modulated X-ray diffractometry applied to a study on calorimetric and structural change of semicrystalline poly(ethylene oxide)

Temperature-modulated X-ray diffractometry (TMXD) has been developed in order to make simultaneous measurement of calorimetry and structure analysis. Simultaneous measurement is useful to compare the thermal properties and structure of materials, which are sensitive to the history of sample preparation. In TMXD, the heat capacity was measured with AC calorimetry and the structure analysis was made with the small-angle X-ray scattering and the wide-angle X-ray diffraction. In this study, TMXD was applied to poly(ethylene oxide) (PEO) to demonstrate the usefulness of the technique. PEO is a semicrystalline polymer in which very thin plate-like crystals coexist with the amorphous regions. PEO is thermodynamically metastable as other semicrystalline polymers and exhibits changes in heat capacity and structure at a constant temperature close to the melting point of the crystals. Time dependences of heat capacity and structure have been measured successfully, and their results were compared in detail.