Polyimide resins with superior thermal stability, dielectric properties, and solubility obtained by introducing trifluoromethyl and diphenylpyridine with different bulk pendant groups

Three polyimides (PI-p, PI-t, and PI-n) containing a 2,6-di(4-aminophenyl) pyridine body and different pendant groups are reported in this study. The resulting polyimide films exhibit excellent dielectric properties, with a dielectric constant of 2.91–2.62@10GHz and a dielectric loss in the range of 0.00939–0.00808@10GHz. Through computer simulation, the dielectric constant and dielectric loss of the polyimides are found to decrease with increasing pendant group volume. Moreover, the resulting strong and flexible polyimide films exhibit excellent thermal stability, with decomposition temperatures (at a 5% weight loss) in the range of 532.3–552 °C and glass-transition temperatures in the range of 343.7–376.4 °C. TGA/FTIR/MS experiments indicate that the thermal stability of the resin containing the methyl phenyl group is worse due to the degradation of the methyl group at low temperatures. In addition, the three polyimides also show excellent solubility and transparency. These superior properties indicate that the PI series is an ideal candidate material for future 5G communications.