A diamine was synthesized by two successive reactions.Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride yielded terephthaloyl bis(4-oxybenzoic) acid.Then reaction of this compound with 1,8-diamino-3,6- dioxaoctane via Yamazaki method resulted in preparation of diamine named terephthalic acid bis(4-{2-[2-(2-amino ethoxy)ethoxy]ethyl carbamoyl}phenyl) ester.After fully characterization it was used to prepare new polyimides through polycondensation with different dianhydrides using trimethylchlorosilane.Characterization of polymers was achieved by common methods and their physical properties including inherent viscosity,thermal behavior,thermal stability,crystallinity and solubility were studied.Prepared polyimides showed improved solubility and good thermal stability. A diamine was synthesized by two generations reactions. Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride yielded terephthaloyl bis (4-oxybenzoic) acid. Reaction of this compound with 1,8-diamino-3,6-dioxaoctane via Yamazaki in preparation of diamine named terephthalic acid bis (4- {2- [2- (2-amino ethoxy) ethoxy] ethyl carbamoyl} phenyl) ester. After fully characterization it was used to prepare new polyimides through polycondensation with different dianhydrides using trimethylchlorosilane. Characterization of polymers was achieved by common methods and their physical properties including prior viscosity, thermal behavior, thermal stability, crystallinity and solubility were studied. Prepared polyimides showed improved solubility and good thermal stability.