Various approaches have been carried out in the synthesis of poly(amide-imide)s. A well-developed solution polycondensation method has been used to prepare such copolymers either from a dianhydride containing a preformed amide group with a diamine or from a dicarboxylic acid containing a preformed imide ring with a diamine. Direct polycondensations of carboxylic acids and aromatic diamines can be a more useful technique for synthesis of poly(amide-imide)s PAIs. In this work, direct polymerization reaction of N,N'-(4,4'-hexafluoroisopropylidendiphthaloyl)-bis-L-isoleucine with several aromatic diamines such as 4,4'-diaminodiphenylsulphone (4a), 4,4'-diaminodiphenylmethane (4b), 4,4'-diaminodiphenylether (4c), 1,4-phenylenediamine (4d), 4,4'-diaminobiphenyl (4e), 1,3-phenylenediamine (4f), 2,4-diaminotoluene (4g), was performed in the presence of tosyl chloride (TsCl)/dimethylformamide (DMF)/pyridine (Py) as a condensing agent. The resulting PAIs were obtained in high yield and inherent viscosity. Some structural characterization and physical properties of these polymers have been studied and will be reported.