A series of soluble novel polyesterimides was synthesized from diamines [a mixture of 2,2-bis(4-(4- aminophenoxy)phenyl)propane (BAPP) with amine-terminated polysiloxane (ATPS) in various mole ratios] and the ester-group-containing dianhydrides. The ester group containing dianhydrides in turn was synthesized by the transesterification reaction of trimellitic anhydride (TMA) with diacetate ester of hydroquinone (HQ), 4,4'-dihydrophenyl (BP), 1,6-hexanediol, or ethylene glycol. The resulted polyesterimides were characterized by using Fourier-transform infrared spectroscopy, inherent viscosity, solubility, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The polyesterimides of BP and HQ had relatively high glass transition temperatures in the range of 214.7-227.2 and 195.7-210.5degreesC, respectively. The glass transitions decreased rather slowly with the increase in polysiloxane content. Thermal stability and the weight-loss behavior of polyesterimides were studied by TGA. All polyesterimides of BP and HQ (BPI and HQI) showed no significant weight loss below 500degreesC in a N-2 environment, and the decomposition temperatures (T-d5%) of BPI and HQI were >520degreesC. Most polyesterimides were soluble in polar aprotic solvents and m-cresol. (C) 2004 Wiley Periodicals, Inc.