The diimide-diacid monomer, N,N'-bis-3-carboxyphenyl)-4,4'-oxydiphthalimide (I), was prepared by azeotropic condensation of 4,4'-oxydiphthalic anhydride and m-aminobenzoic acid at a 1:2 molar ratio in polar solvent: and toluene. A series of organosoluble and colorless poly(amide-imide)s with inherent viscosities ranging from 0.95 to 1.70 dl/g were synthesized from diimide-diacid I and various aromatic diamines by the direct polycondensation using triphenyl phosphite and pyridine as condensing agents. From UV-visible spectrum and resulting parameters of Macbeth Color-eye colorimeter, these polymers were much lighter in color than other analogous polymers. All the poly(amide-imide)s were readily soluble in a variety of organic solvents such as NMP, DMAc, DMF, and DMSO, and some even could be dissolved in less polar solvents such as m-cresol and pyridine. The cast films exhibited tensile strengths ranging from 82 to 106 MPa, elongations to break from 10 to 15%, and initial moduli from 1.9 to 2.3 GPa. Poly(amide-imide)s had glass transition temperatures of 221-276 degreesC and 10% weight loss temperatures of 551-570 degreesC in nitrogen and 548-578 degreesC in air indicating excellent thermal stability. (C) 2001 Elsevier Science Ltd. All rights reserved.