Tailoring dielectric properties of poly(arylene ether nitrile) via bisphthalonitrile prepolymer morphology control

With the development of electronic devices to high frequency and miniaturization, the insufficient voltage resistance of insulating polymers has become a key bottleneck. Here, a morphological gradient of bisphthalonitrile (BPh) prepolymer was designed to optimize the dielectric properties of polyarylene ether nitrile (PEN). Specifically, BPh prepolymers with different morphologies were prepared by the high-temperature solvothermal method (160 ℃): 1 h to generate a sheet structure, 3 h to form a lamellar-spherical mixed structure, and 6 h to form a spherical structure. After the composite film was prepared by filling the prepolymer into PEN, the film was then prepared by curing reaction and its dielectric properties were investigated. Results show that breakdown strength of cured composite with sheet prepolymer is 343.11 kV/mm, which is 111.91 % higher than that of pure PEN (161.91 kV/mm). The lamellae-spherical (188.36 kV/mm) and spherical (238.07 kV/mm) structures increased by 16.34 % and 47.03 %, respectively. It means that the sheet structure can effectively disperse the electric field, while the spherical structure has a weak inhibition ability due to the curvature effect. This work provides a new idea for the design of highly insulating polymer films.