A new aromatic diamine monomer, 2,2′-bis[3,5-di(4-trifluoromethylphenyl)-4-(4-aminophenoxy)phenyl]sulfone, containing four pendant trifluoromethylphenyl group substituents was successfully synthesized via a three-step reaction from readily available reagents. A new series of fluorinated polyimides with multi-bulky pendant groups was prepared from the diamine monomer with three commercially available aromatic tetracarboxylic dianhydrides using one-step high-temperature polycondensation. The incorporation of multi-bulky pendant fluorinated groups and large non-coplanar structures brought about a great improvement in their properties. The resulting polyimides had excellent solubility and the maximum solubility even reached 20 wt% in NMP, CHCl3, and THF at room temperature. Their film displayed a light color and high optical transparency with the cut-off wavelengths ranging from 327 to 343 nm. They also possessed intrinsically low dielectric constant values of 2.69–2.85 (at 1 MHz) and low water absorption (0.59–0.68%). Moreover, these polyimides showed high glass transition temperatures (259–281 °C) and excellent thermal stability with 5% weight loss at temperatures over the range of 551–561 °C and 515–520 °C under nitrogen and air atmospheres, respectively. Compared to some trifluoromethyl-substituted polyimides, these polyimides with multi-bulky pendant groups possessed better solubility and lower cut-off wavelength and dielectric constants.

A series of fluorinated polyimide/POSS hybrid polymers (FPI-4-FPI-16) were prepared via a facile synthetic route using 2,2'-bis(trifluoromethyl)benzidine, 4,4'-oxydiphthalic dianhydride and monofunctional POSS as starting materials. The hybrid polymers showed excellent solubility and film formation ability. Flexible and robust hybrid films could be conveniently obtained via solution-casting. The hybrid films demonstrated low dielectric constants and high thermal stability. Their dielectric constants were in the range of 2.47–2.92 at 1 MHz measured for their capacitance, and were tunable and decreased with an increase of POSS content. Their 10% weight loss temperatures were in the range of 539-591 °C and the weight residual at 800 °C ranged from 48% to 53% in nitrogen atmosphere. These hybrid films also possessed good mechanical properties and hydrophobic characteristics. This work could provide a potential strategy for the preparation of fluorinated polyimide/POSS hybrid polymers.

•Sulfonated aromatic polyamides containing nitrile groups were reported.•The strong interactions and hydrogen bonds played an important role for properties.•The membranes had good balance between dimensional stability and proton conductivity.A series of sulfonated aromatic polyamides containing nitrile groups (SPA-xx) were prepared by the phosphorylation polyamidation using 2,6-bis(4-aminophenoxy)benzonitrile, 5-sulfoisophthalic acid sodium salt and terephthalic acid as starting materials. The intrinsic viscosities of these polymers were between 1.23 and 2.16 dL/g. All the sulfonated polymers have good solubility and could afford flexible proton exchange membranes by solution-casting. Their chemical structures were characterized by fourier transformation infrared spectrum (FTIR) and nuclear magnetic resonance spectrum (NMR). Their properties, including water uptake, dimensional change, proton conductivity and thermal and chemical stability, were also investigated in detail. The results indicated that these sulfonated aromatic polyamides had good dimensional stability and chemical stability, proton conductivity and thermal stability. The representative SPA-100 membrane with IEC values of 1.87 mequiv./g, showed swelling ratio of 16.5% and proton conductivity of 141 mS/cm at 80 °C, respectively.