Synthesis and characterization of novel star-branched polyimides derived from 2,2-bis[4-(2,4-diaminophenoxy) phenyl] hexafluoropropane

A novel aromatic fluorinated tetramine, 2,2-bis[4-(2,4-diaminophenoxy) phenyl] hexafluoropropane (BDAPFP), was successfully synthesized. To maximize the advantages of the linear polyimides and hyperbranched polyimides, a series of novel star-branched fluorinated polyimides BPI-(1-3), which were derived from BDAPFP and anhydride-terminated linear poly(amide acid) s LPAA'-(1-3), were successfully synthesized. For comparison, a series of corresponding linear polyimides LPI-(1-3) were prepared from 4,4'-oxybisbenzenamine (ODA), p-phenylenediamine (PDA) and 3,30,4,4'-biphenyltetracarboxylic dianhydride (BPDA) with various monomer ratios via the conventional two-step procedure with heating, imidization method. All the polyimides could form strong, flexible and transparent films with an UVvisible absorption cut-off wavelength at 366-398 nm. When compared with the linear polyimide films LPI-(1-3), the star-branched fluorinated polyimide films BPI-(1-3) not only possessed better thermal stability with glass transition temperatures of 283.0-318.0 degrees C and 5% weight loss temperatures of 544578 degrees C and 500-560 degrees C in nitrogen and air, respectively, but also had improved mechanical properties with tensile strengths of 113-243 MPa, elongation at break of 9.44-9.70% and tensile modulus of 2.093.74 GPa. Moreover, the star-branched polyimide films BPI-(1-3) exhibited lower water absorptions of 0.35-0.52%, better dielectric properties with lower dielectric constants of 2.72-3.12 and lower dielectric losses of 0.0028-0.0040 at 1000 kHz.