Novel polyfluorinated polyimides derived from α,α-bis(4-amino-3,5-difluorophenyl)phenylmethane and aromatic dianhydrides: Synthesis and characterization

A novel aromatic diamine containing bulky lateral phenyl unit and fluorine groups ortho-substituted to the amino groups in the structure, α,α-bis(4-amino-3,5-difluorophenyl)phenylmethane (4FMA) was synthesized and characterized. 4FMA was polymerized with four aromatic dianhydrides to afford a series of polyimides (PIs) via a one-step high-temperature polycondensation procedure. All the PIs were amorphous and showed good solubility not only in polar aprotic solvents, but in many common solvents, such as cyclopentanone and tetrahydrofuran. The soluble polymers formed flexible, tough and transparent films. The films had a tensile strength, elongation at break, and tensile modulus in the ranges 85–107 MPa, 4–7%, 1.7–2.8 GPa, respectively. The polyimides also exhibited high-Tg (292–338 °C), good thermal stability, good dielectric strength, low dielectric constants, and low water uptakes due to the introduction of the polyfluorinated substituents in the polymer backbone. As expected, the PI films showed good transparency in the UV–Vis light region with cutoff wavelength as low as 318 nm and transmittance higher than 60% at 450 nm. PI-4 derived from 4FMA and fluorinated dianhydride 6FDA exhibited low light-absorption in the near-infrared region, especially at the optocommunication wavelength of 1310 nm and 1550 nm. The remarkable combined properties indicate their potential applications in microelectronic and optoelectronic fabrications.