Thermal stability and structural anisotropy of semiaromatic poly(ester amides) from aromatic bis(2-oxazolines) and aliphatic dicarboxylic acids

Semiaromatic poly(ester amides) containing three different aromatic units and aliphatic spacers with five different chain lengths were investigated using various experimental methods, with a focus on the effect of structural changes in the mesogenic groups and the length of the flexible alkylene spacer on the observed physical properties. The results of thermal stabilities and crystallographic measurements indicate that the thermal stability is dependent on the content of the amorphous phase in the polymer. The results from the thermal stability, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and optical microscopy of the poly(ester amides) containing aromatic moieties were compared to the dielectric properties recorded using dielectric relaxation spectroscopy (DRS). DRS contributed to the description of four relaxation regions detected by matching the temperature and frequency dependencies of the dielectric functions. For the poly(ester amides) containing biphenyl units, the presence of a liquid-crystalline (LC) phase was observed.