Paracrystalline Nature of Poly (p-Phenylene)

The electron diffraction pattern of oriented, annealed poly (p-phenylene) is explained on the basis of an orthorhombic unit cell: a = 0.7781, b = 0.5520 and c(fiber axis) = 0.4300 nm. and exhibits the following features:

(1)The reflections on the equator and meridian are sharp. Only a few weak diagonal reflections can be observed.

(2) Strong diffuse scattering is seen on the third layer line.

(3)The reflections on the meridian (00l-reflections) have a characteristic line profile. in which the intensity increases suddenly at the Bragg angle and decreases gradually.

From (1) to (3), it can be concluded that the material is paracrystalline like a nematic structure in liquid crystals. Molecular chains are laterally packed in a rather regular way. However, the disorder by the shift of chains in the direction parallel to their axes is remarkable.