A novel non-coplanar aromatic diamine monomer,3,3'-ditertbutyl-4,4'-diaminodiphenyl-4''-naphthylmethane(TAPN) was synthesized by a condensation reaction of 2-tertbutylaniline and 1-naphthaldehyde under catalyst hydrochloric acid.The structure of the monomer was confirmed by FTIR,NMR,elementary analysis and mass spectrometry.A series of aromatic polyimides(PIs) were synthesized via conventional one-step polycondensation from TAPN and various commercial aromatic dianhydrides.All of the PIs exhibit excellent solubility in common organic solvents,even in low boiling point solvents such as chloroform(CHCl3),tetrahydrofuran(THF) and acetone.The PIs present outstanding thermal stability with the glass transition temperature(Tg) ranged from 299 °C to 350 °C,and the temperature at 10% weight loss ranged from 490 °C to 504 °C,and high optical transparency with the cutoff wavelengths of 306-356 nm.Moreover,the flexible and tough PI films have prominent mechanical properties with tensile strengths in the range of 77.6-90.5 MPa,tensile modulus in the range of 1.8-2.4 GPa and elongation at break in the range of 6.3%-9.5%,as well as lower dielectric constant(2.89-3.12 at 1 MHz) and lower moisture absorption(0.35%-0.66%).
