화학공학소재연구정보센터
Journal of Chemical Physics, Vol.103, No.13, 5762-5766, 1995
Solid-Solid Phase-Transitions in N-Alkanes C23H48 and C25H52 - X-Ray Power Diffraction Study on New Layer Stacking in Phase-V
The solid-solid phase transitions and the crystal structures of odd n-alkanes, n-C23H48, and n-C25H52, were investigated by x-ray powder diffraction. The phase transitions, I-->V-->RI for n-C23H48 and I-->V-->IV-->RI for n-C25H52, were observed, where phases I, V, TV are the low-temperature ordered phases, and the phase RT is the rotator phase. The crystal structure of phase V was determined by the Rietveld profile refinement method. Phase V is orthorhombic (P-bnm). New molecular layer stacking appears in phase V, while the lamellar structure and the lateral packing of molecules are same as those in phase I and phase IV. The solid-solid phase transitions below the rotator phase transition of odd n-alkanes found to be characterized by the changes in molecular layer stacking are considered to be caused by the increased disorder in the layer surface.