Abstract:An aromatic diamine with asymmetric structure and trifluoromethyl substitution, 2,5-bis(aminobenzene)benzotrifluoride, was successfully synthesized by two-step organic reaction using 2,5-dibromobenzotrifluoride and 3-nitrophenylboronic acid as starting material. A series of new polyimides (PI 4a~PI 4d) were produced via one-step high-temperature polycondensation, using this diamine and four commercial aromatic dianhydrides. The molecular structures for the diamine monomer and polyimides were characterized by infrared and nuclear magnetic resonance spectroscopy. The polyimide PI 4b~PI 4d cannot only be dissolved in DMAc, NMP, DMSO with polar high-boiling solvents at room temperature, but also can be conveniently coated with a polymer solution to obtain films. And PI 4b has the best solubility and could be soluble in low boiling point solvents such as CHCl3, CH2Cl2. These polyimides have good thermal properties, and their 5% mass loss temperatures both in N2 and O2 are above 498 ℃ and the glass transition temperatures are above 240 ℃. And their tensile strength for polymer films are in the range of 77.4~88.6 MPa, the elastic modulus is within the scope of 2.0~2.9 GPa, and the elongation at break are within 4.9%~9.9%. Moreover, their optical transmittance is higher than 67% at 450 nm and the cut-off wavelength is in the range of 329~357 nm.