The one-pot, high temperature, catalytic synthesis of polyetherimides (PEIs) in molten benzoic acid was investigated. The synthesis was conducted using the AB monomers, 4-aminophenoxy phthalic acid (IIa) and 3-aminophenoxy phthalic acid (IIb). Both Homo and co-PEIs with different ratios of substituted AB IIa and IIb were prepared and characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry and wide angle X-ray diffraction. The solubility of the polymers in a variety of solvents was also investigated. Homo-poly-lib is an amorphous thermoplastic that is soluble in CHC13 DMS8 and amide-type solvents. Homo-poly-IIa has a locally ordered structure and is insoluble. Properties of the IIa/IIb copolymers depend strongly on their composition. When the IIa/Hlb ratio is 30: 70 or less, co-PEIs behave as thermoplastic substances soluble in chloroform. At an IIa/lIb ratio in the starting mixture of 40: 60 or higher, the properties of co-PEIs are similar to that of poly-IIa.