Polymer composites with balanced dielectric constant and loss via constructing trilayer architecture

Polymers with high dielectric constants are widely used in electronic devices and electric systems. However, polymers exhibit low dielectric constants, which greatly limit their applications. Currently, ferroelectric ceramic fillers and conductive filler are commonly filled into polymer matrix to achieve enhanced dielectric constants. Unfortunately, even though the loading fraction of ferroelectric ceramic fillers exceeds 50 vol%, the enhancement of dielectric constant is still limited. On the contrary, although ultrahigh dielectric constant could be realized in conductor/polymer composites containing small loading fractions of conductive fillers, the loss is usually very high owing to severe leakage conduction. To overcome the shortcomings of the above-mentioned two types of high dielectric composites, this work combined them together and designed a series of trilayer polymer composites consisting of one carbon nanotube/polyimide composite layer sandwiched by two BaTiO3/polyimide composite layers. Fortunately, the trilayer architecture could effectively overcome the drawbacks of carbon nanotube/polyimide and BaTiO3/polyimide single-layer composites, hence the balanced dielectric constant and loss. When the BT content of the outer layer is 50 wt% and the carbon nanotube content of the middle layer is 4 wt%, the trilayer film possesses a high dielectric constant of ~ 35 @10 kHz, which is about 700% over pristine PI matrix (e′ ≈ 5 @10 kHz). Meanwhile, the loss tangent of the trilayer composite (tanδ ≈ 0.03 @10 kHz) is still comparative to pristine PI (tanδ ≈ 0.01 @10 kHz).