X-RAY-ANALYSIS OF THE STRUCTURE OF THE THERMOTROPIC COPOLYESTER XYDAR

The structure of the thermotropic copolyester prepared from p-hydroxybenzoic acid (HBA), terephthalic acid (TPA), and biphenol (BP) has been investigated by X-ray diffraction methods. This chemical formulation is the basis of the XYDAR family of resins. X-ray fiber diagrams for four HBA/TPA/BP comonomer ratios show high orientation and the presence of three-dimensional order. The meridional region contains a series of aperiodic maxima that shift in position with the composition. These are reproduced in predictions of the scattering intensity for a nematic array of chains of completely random monomer sequence. The polymer chains have highly extended conformations, as a result of the linearity of the linkage bonds and the planarity of the aromatic and carboxyl groups.