Fluorinated diimide-dicarboxylic acid (DIDA, Code: IV), 1,4-bis(4-trimellitimido-2-trifluoromethylphenoxy) benzene, synthesized by reacting 1,4-bis(4-amino-2-trifluoromethyl phenoxy)benzene (1) with trimellitic anhydride in polar solvents (PSv), was found to crystallize easily in amide-type solvents, such as N-methyl-2-pyrrolidinone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), or 1,3-dimethyl-2-imidazolidinone (DMI) media, to form a series of stable crystalline solvates (III(NMP), III(DMAc), IIIDMF), III(DMI)) containing a certain quantity of crystalline solvent. The solvates III(PSv) were characterized and proven by DSC, TGA, and X-ray analysis. The decomposition point temperature (T-d) was different with the type of polar solvents in III(PSv). Elemental analysis and NMR showed that most of the III(PSv) were formed from IV and polar solvents in the ratio of 1:2, and the solvation processes were found to be reversible. Furthermore, a series of soluble fluorinated poly(amide-imide)s (VIn-h) were synthesized from reacting either the NMP-solvates III(NMP) or dry/non-solvates IV with an equivalent amount of diamines by direct polycondensation using triphenyl phosphate and pyridine as condensing agents. Thermal and mechanical properties of the fluorinated VIn-h were measured, and compared with counterparts of nonfluorinated PAI's (Code: VI's). In comparison, the fluorinated VIn-h poly(amide-imide)s exhibited better solubility, tensile, and thermal properties than the non-fluorinated VI's. (C) 2004 Elsevier Ltd. All rights reserved.