A new-type of dicarboxylic acid was synthesized from the reaction of 2,5-bis(4-aminobenzylidene)cyclopentanone with trimellitic anhydride in a solution of glacial acetic acid/pyridine (Py) at refluxing temperature. Six novel heat resistance poly(amide-imide)s (PAIs) with good inherent viscosities were synthesized, from the direct polycondensation reaction of N,N'-[2,5-bis(4-aminobenzylidene) cyclopentanone]bistrimellitimide acid with several aromatic diamines, by two different methods such as direct polycondensation in a medium consisting of N-methyl-2-pyrrolidone (NMP)/triphenyl phosphite (TPP)/calcium chloride (CaCl(2))/pyridine (Py) and direct polycondensation in a p-toluene sulfonyl chloride (tosyl chloride, TsCl)/pyridine (Py)/N,N-dimethylformamide (DMF) system. All of the above polymers were fully characterized by (1)H NMR, FTIR, elemental analysis, inherent viscosity, solubility tests, UV-vis spectroscopy, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and derivative of thermaogravimetric (DTG). The resulted poly(amide-imide) s (PAIs) have showed admirable good inherent viscosities, thermal stability, and solubility. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2877-2885, 2011