A dicarboxylic acid {1,1-bis[4-(4-trimellitimidophenoxy)phenyl]-1-phenylethane (II)} bearing two performed imide rings was prepared from the condensation of 1,1-bis [4-(4-aminophenoxy)phenyl]-1-phenylethane and trimellitic anhydride in a 1/2 molar ratio. A novel family of poly(amide-imide)s with inherent viscosities of 0.83-1.51 dL/g was prepared by triphenyl phosphite-activated polycondensation from the diimide-diacid II with various aromatic diamines in a medium consisting of N-methyl-2-pyrrolidinone (NMP), pyridine, and calcium chloride. Because the 1,1,1-triphenylethane group of II was unsymmetrical, most of the resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP and N,N dimethylacetamide. All the soluble poly(amide-imide)s afforded tough, transparent, and flexible films, which had tensile strengths ranging from 88 to 102 MPa, elongations at break from 6 to 11%, and initial moduli from 2.23 to 2.71 GPa. The synthesized poly(amide-imide)s possessed glass-transition temperatures from 250 to 287 degreesC. The poly(amide-imide)s exhibited excellent thermal stabilities and had 10% weight losses from 501 to 534 degreesC under a nitrogen atmosphere. A comparative study of some corresponding poly(amide-imide)s is also presented. (C) 2001 John Wiley & Sons, Inc.