| Abstract: | The molecular structure of poly (p-hydroxybenzoic acid) (C6H4COO)x at ambient temperature was determined by x-ray powder diffraction analysis. The diffraction pattern is explained as a mixture of two orthorhombic phases having the same space group Pbc21 with four C6H4COO chemical repeats in the unit cell and the following cell parameters: a = 7.42 Å, b = 5.70 Å, and c = 12.45 Å for phase I (ρcalc = 1.51 g cm?3); and a = 3.83 Å, b = 11.16 Å, and c = 12.56 Å for phase II (ρcalc = 1.48 g cm?3). The chain conformation is the same in both phases, involving two benzoyl rings staggered by ca. 120° along the chain. Disorder has been considered in the packing of phase I by giving equal occupancy to the two molecules oriented up or down along the c chain axis. ©1995 John Wiley & Sons, Inc. |
