On the structure and thermo-mechanical properties of a thermotropic liquid crystalline copolyester amide

Abstract

The microstructure at Å- and nm-scale of a thermotropic liquid crystal copolyester amide has been studied by wide-angle and small-angle X-ray scattering (WAXS and SAXS, respectively). The copolyester amide is based on random monomers of 60 mol% 2,6-hydroxynaphthoic acid, 20 mol% terephthalic acid and 20 mol% amino phenol (designated N-T-AP). In the solid state the copolyester amide is unusually crystalline and the WAXS fiber pattern exhibited equatorial and off equatorial reflections indicative of lateral packing and relative three-dimensional order. Moreover, the pattern also exhibited meridional scattering maxima and the position was aperiodic, a property also reported for the thermotropic random copolyester of 1,4-hydroxy benzoic acid and 2,6-hydroxynaphthoic acid. The meridional scattering was well-modeled by a totally random arrangement of monomers in a straight conformation, where a polymer chain was modeled by an array of points separated by the corresponding monomer length. Hence, the data is consistent with a structure formed by highly aligned macromolecules of totally random monomer sequence. Furthermore, the meridional maxima indicate monomer sequence segregation which would lead to the formation of crystallites, and the sequence segregation is reminiscent of a non-periodic layer crystal (npl).