A series of random poly(amideimide)s (PAIs) were prepared from 1,2,4-benzenetricarboxylic acid monoesters and multi-ring diamines containing bisaryloxy groups by a ’one pot’ method using the triphenylphosphite/pyridine system. The diamines differ because of the para or meta catenation and because of the presence of lateral substituents or bulky isopropylidene or perfluoroisopropylidene groups connecting two phenyl rings. The prepared PAIs were characterized by Fourier transform infra-red and H-1 nuclear magnetic resonance spectroscopy. Thermal analysis and X-ray diffraction experiments indicated that all PAIs ’as polymerized’, are amorphous and that polymers having a prevailing para-orientation and no substituents crystallize upon thermal treatments. The glass transition temperatures (T(g)s) determined by differential scanning calorimetry and dynamic mechanical thermal analysis, range between 178 degrees C and 253 degrees C. Both the T-g and the solubility, in polar aprotic solvents, are strongly affected by the chemical structure of the polymers. Flexible and tough films were obtained by solution casting or, in the case of amorphous PAIs, by compression moulding. The PAIs investigated exhibit thermostability-10% weight loss at T greater than or equal to 495 degrees C-as shown by dynamic thermogravimetric analysis.