Synthesis and characterization of polyimides from bis(3-aminophenyl)-2,3,5,6-tetrafluoro-4-trifluoromethylphenyl phosphine oxide (mDA7FPPO)

A novel diamine, bis(3-aminophenyl)-2,3,5,6-tetrafluoro-4-trifluoromethylphenyl phosphine oxide (mDA7FPPO), was synthesized via Grignard reaction, followed by nitration and reduction. The monomer was characterized by FT-IR, NMR and melting point apparatus, and utilized to prepare polyimides with 6FDA, BTDA or ODPA via a conventional two-step synthesis; preparation of poly(amic acid), followed by solution imidization. The molecular weight of polyimides was controlled to 20,000 g/mol by off-stoichiometry and the polyimides were characterized by FT-IR, NMR, GPC, TGA and DSC. Solubility, intrinsic viscosity, dielectric constant and refractive index were also evaluated. The novel polyimides exhibited high Tg (229-252 °C), excellent thermal stability (>500 °C), low dielectric constant (2.65-2.81) and low birefringence (0.0019-0.0049).