Crystal structure of poly(octamethylene terephthalate) determined by X-ray fiber diffraction and molecular modeling

Poly(octamethylene terephthalate) (POT), a semicrystalline aromatic polyester, is synthesized by melt-condensation reaction, and its thermal property and crystal structure are investigated by using differential scanning calorimetry, X-ray diffraction, and molecular modeling methods, respectively. It is revealed that the synthesized POT sample has comparably low melting temperature of 131 °C and forms one crystalline phase. Based on two-dimensional X-ray fiber diagram and molecular modeling analyses, the crystal structure of POT is identified to be triclinic with dimensions of a = 4.560 A, b = 5.597 A, c = 18.703 A, α = 104.87°, β = 119.45°, and γ = 100.32°, in which one chemical repeating unit of POT with all-trans conformation of octamethylene group is packed according to the space group of . © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 276–283, 2009