A new mesogene diester based on phenyltrimellitimide was synthesized and used as a condensation monomer in combination with a number of aliphatic diols to render novel poly(ester-amide-imide)s (PEAIs). The melt polycondensation method provided polymers of moderate inherent viscosity, that were characterized by elemental analyses, differential scanning calorimetry, X-ray diffractometry, including synchrotron radiation measurements at different temperatures, optical microscopy with polarized light and thermogravimetric analysis. The glass transition temperatures (T-g) lie in the range 100-130 degrees C, which means a substantial improvement relative to analogous poly(ester-imide)s (PEIs). All the novel PEAIs are thermotropic materials that show a mobile LC-mesophase above the melting temperature. By combining microscopic observations with X-ray diffraction diagrams, the mesophases could be identified as smectic-A phases. PEAIs with even-numbered spacers are semi-crystalline in the solid slate, while those with odd-numbered spacers can form a solid smectic glass phase, i.e, a frozen smectic-A phase, upon rapid cooling from the melt.