A new monomer of tetraimide-dicarboxylic acid (IV) was synthesized by starting from ring-opening addition of 4,4'-oxydiphthalic anhydride, trimellitic anhydride, and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene at a 1:2:2 molar ratio in N-methyl-2-pyrrolidone (NMP). From this new monomer, a series of novel organosoluble poly(amide-imide-imide)s with inherent viscosities of 0.7-0.96 dL/g were prepared by triphenyl phosphite activated polycondensation from the tetraimide-diacid with various aromatic diamines. All synthesized polymers were readily soluble in a variety of organic solvents such as NMP and N,N-dimethylacetamide, and most of them were soluble even in less polar m-cresol and pyridine. These polymers afforded tough, transparent, and flexible films with tensile strengths ranging from 99 to 125 MPa, elongations at break from 12 to 19%, and initial moduli from 1.6 to 2.4 GPa. The thermal properties and stability were also good with glasstransition temperatures of 236-276 degrees C and thermogravimetric analysis 10 wt % loss temperatures of 504-559 degrees C in nitrogen and 499-544 degrees C in air. 2006 Wiley Periodicals, Inc.