Polyimide dielectric nanocomposites containing functional nanofillers based on multilayer structure: Design, preparation, and properties

Polyimide (PI) dielectric nanocomposites containing functional nanofillers based on layered structure (single-layer: BT@Al 2 O 3 @PI, double-layer: PI/BT@Al 2 O 3 @PI, three-layer: PI/BT@Al 2 O 3 @PI/PI) were designed and prepared by using PI as matrix, barium titanate (BT)@alumina (Al 2 O 3 ) as nanofillers through in-situ polymerization compounding technology. FTIR tests indicated that PI and PI dielectric nanocomposites have been synthesized successfully. The molecular mass of BaTiO 3 @Al 2 O 3 @PAA oligomer was higher than that of pure PAA when BT and Al 2 O 3 nanofillers were incorporated simultaneously, as verified by GPC and intrinsic viscosity tests. XRD analysis showed that the addition of nanofillers destroyed the order of PI molecular structure and reduced the arrangement density of PI molecular chains. Both FESEM and HRTEM observations showed that the nanofillers were homogeneously dispersed in the PI matrix, contributing to the property improvements of PI dielectric nanocomposites. TGA results indicated that adding nanofillers improved the thermal stability and heat resistance of PI dielectric nanocomposites. The dielectric constant of PI/BT@Al 2 O 3 @PI double-layer nanocomposites was between the single-layer nanocomposites and pure PI. Due to the effective medium theory, the dielectric constant of three-layer PI/BT@Al 2 O 3 @PI/PI nanocomposites containing 5 wt% BT@Al 2 O 3 reached 5.43. This work can be expected to provide an effective strategy to fabricate PI dielectric nanocomposite films for energy storage applications.