Crystal Structure of Poly(octamethylene terephthalate) Determined by X-Ray Fiber Diffraction and Molecular Modeling

Abstract

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 degrees 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 angstrom, b = 5.597 angstrom, c = 18.703 angstrom, alpha = 104.87 degrees, beta = 119.45 degrees, and gamma = 100.32 degrees, in which one chemical repeating unit of POT with all-trans conformation of octamethylene group is packed according to the space group of P (1) over bar. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys 47: 276-283, 2009