Electron diffraction and computer modeling studies of the crystal structure of poly(butylene terephthalate) alpha-form single crystals

Lamellar alpha-form single crystals of poly(butylene terephthalate) (PET) have been prepared by our confined thin film melt polymerization method at polymerization temperatures of 190 degrees to 210 degrees C. These lamellar PET single crystals have a thickness of ca. 100 Angstrom, with (010) twinned crystals frequently observed. Six different zonal electron diffraction patterns were obtained, from which the lattice parameters are determined as a = 4.94 Angstrom, b = 5.98 Angstrom, c = 11.56 Angstrom, alpha = 99.8 degrees, beta = 116.5 degrees, and gamma = 111.1(5) degrees with a volume of 261.86 Angstrom(3), corresponding to a calculated density of 1.397 g/cm(3) for this ''perfect'' PET single crystal. Chain packing and molecular conformation in the triclinic unit cell (space group <P(1)over bar>) were simulated by the Cerius(2) modeling software.