Abstract: In this paper， a type of high-temperature-resistant polyimide （PI） resins terminated with phenylethynyl groups was prepared by using 2，3，3'，4'-diphenyl ether tetracarboxylic acid dianhydride and 9，9-bis（4-aminophenyl） fluorene as raw materials. The relationships between the chemical structure of the as-prepared products and their solubility， curing properties， and heat resistance were investigated by using Fourier-transform infrared spectroscopy， differential scanning calorimetry， and thermogravimetric analysis， and the relevant influencing mechanisms were studied. The results indicated that the oligomers had high solubility in organic solvents. The as-prepared PI resin samples exhibited a maximum glass transition temperature of 356 ℃， which increased by 41 oC with increasing the fluorenyl content. The cured PI resins presented a high thermal stability with a 5 wt% thermogravimetric temperature of above 520 ℃ in nitrogen， and their residual char yields were as high as 60 wt% at 800 ℃. The thermoset PI resins gained an improvement in temperature resistance and were expected to be applied in marine engineering equipments， national defense， military industry， and other fields.

Key words: thermoset polyimide, 4-phenylethynylphthalic anhydride, fluorenyl group, thermal resistance