A novel end cap 3-trifluoromethyl-4-(phenylethynyl)aniline (3FPA) was obtained by reduction of the corresponding nitro-compound which was synthesized by coupling of 2-trifluoromethyl-4-nitro-1-bromobenzene with ethynylbenzene.Polyimide monomer solutions were prepared by classic PMR process using p-phenylenediamine (p-PDA)

the diethyl ester of 4

4′-hexafluoroisopropylidene-bisphthalic acid (6FDE) and 3-trifluoromethyl-4-(phenylethynyl) aniline as endcap.The monomer solution has high solid contents of about 40%～45%

low viscosity of about 28～36 mPa·s and show high stability at room temperature in two months.The polyimide molding powders were produced by thermally curing the monomer solutions at 200℃

and the imidization degree of powders increased with increasing the curing temperature. The thermosetted polyimides were produced by thermal curing the polyimide molding powders at 370℃ under pressure of 1～2 MPa.The postcured polyimide showed a 5% weight loss temperature of 536℃ and Tg about 404℃(DMA).The thermo-oxidative stability of the thermosetted polyimides 3FPA-PI-50 and PMR-Ⅱ resins at elevated temperature (370℃) were determined by isothermally aging the samples in flowing air atmosphere

and the weight loss of 3FPA-PI-50 was about 6.78 wt% after 300 h isothermal aging which was lower than that of PMR-Ⅱ(7.15%).