Enhanced high-temperature capacitive performance through introduction of polar groups in poly(aryl ether ketone) dielectric polymer

High-temperature poly(aryl ether ketone) dielectrics have attracted application prospects in the field of polymer film capacitors. However, the investigations on improving the capacitive properties of poly(aryl ether ketone) based on molecular structure design strategies were absent. Herein, a series of poly(aryl ether ketone) bearing phthalazinone moiety were synthesized, and the effect of chemical structures on the capacitive properties of the resultant polymers was investigated by experimental data and density functional theory calculation. The introduction of the sulfone group could not only improve the permittivity but also construct deep carrier traps to enhance the breakdown strength, leading to high discharge energy density (Ue) value of the poly(phthalazinone ether sulfone ketone) (PPESK). For the poly(phthalazinone ether nitrile ketone) (PPENK), the introduction of the nitrile group could improve the Ue at room temperature, but reduce the value at elevated temperatures. As a result, at room temperature, the maximum Ue of both the PPESK (4.56 J/cm3) and the PPENK (3.40 J/cm3) was higher than that of the PPEK (3.02 J/cm3). Notably, the maximum Ue of the PPESK reached 3.07 J/cm3 at 150 °C, which is twice that of commercially bi-oriented polypropylene (BOPP) film (1.5 J/cm3 at 70 °C). Additionally, at the electric field of 200 MV/m and 150 °C, the PPESK films exhibited the Ue of 0.72 J/cm3 with charge-discharge efficiency (η) of 97.2 %, which was obviously superior to those of the BOPP (Ue = 0.4 J/cm3 with η of 96 % at 70 °C). This study presents an in-depth analysis regarding the relationship between the sulfone and nitrile groups and the capacitive performance of poly(aryl ether ketone) bearing phthalazinone moiety, which is informative for designing high-temperature dielectric polymers.