Development of new materials for high energy density capacitor is of great importance to provide high power needed for hybrid electric vehicles, high energy lasers, electromagnetic railguns, etc. Biaxially oriented polypropylene (BOPP) has dominated the market as the primary choice for energy storage capacitors, but it shows a relatively low dielectric constant (~ 2.2) and reduced breakdown strength above 80oC. Herein, new materials are investigated for replacement of BOPP, but it is challenging to achieve a high dielectric constant as well as low dielectric loss. Polyimides are promising for next generation polymer dielectrics due to their higher polarizability and better thermal stability. Rationally designed polyimide thin films with polyether segments were prepared with high dielectric constants up to 7.8, while maintaining low loss (<1%) at temperatures higher than 100 oC. Our syntheses were guided by high-throughput density functional theory (DFT) calculations and the experimental measurements were found to be in close agreement with the theoretical calculations. Variations on the polyimide structure allowed for a clear demonstration of the relationship between chemical functionalities and dielectric properties in terms of dielectric constant, dielectric loss, band gap, etc. Dielectric properties were found to be greatly dependent on conjugation structures and the length of polyether segment in the polyimide backbone.

Rationally designed polyimide thin films for high energy density capacitor applications

247th National Meeting (2014)

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