Development of high dielectric polyimides containing bipyridine units for polymer film capacitor

Polymer dielectrics with high dielectric constant, low dielectric loss, high breakdown strength, and high temperature capability are attractive for applications such as capacitive energy-storage. Commercially available polymer dielectrics such as biaxially oriented polypropylene (BOPP), poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), polycarbonate (PC), and poly(vinylidene) fluoride (PVDF) can be just operated below 200 °C. Great effort has been put into exploring high temperature polymer dielectrics to fulfill the demand of high temperature applications, such as the aerospace and military power supply. In this study, a series of polyimides containing bipyridine units with good dielectric performance and high temperature capability were prepared by using a newly synthesized diamine monomer, (5,5′-bis [(4-amino) phenoxy]-2,2′-bipyridine (BPBPA)). These polyimides possessed high dielectric constant of the as-synthesized polyimides can be up to7.2, the dielectric loss was < 0.04, and the energy density was up to 2.77 J/cm3. Furthermore, the polyimides exhibited high glass transition temperature (Tg) of 275-320 °C and tensile strengths of 175-221 MPa. These obtained polyimides promise potential applications in high temperature flexible polymer film capacitor operated at high temperature.