Partially fluorinated metallic surface constructing robust, thermally conductive and electrically insulating polymer composite

Metallic fillers have shown limited potential for developing advanced polymer substrates for flexible electronics due to their electrical conductivity and poor interfacial interaction with polymers, despite their excellent thermal conductivity (λ). Here, metallic aluminum powders (APs) after surface modification were selected as thermally conductive fillers to modify polyimide (PI) films. We constructed a partially fluorinated alumina layer (PFAL) on the APs surface by employing direct fluorination of F2/N2 mixture. It was demonstrated that the new core-shell structure equipped the fluorinated APs (FAPs) with much better dispersibility and stronger interaction with polyamide acids (PAAs) and PIs bulk, in contrast to APs. Even when the loading of FAPs was up to 50 wt%, the tensile strength of PI/FAPs still remained at a high value of 87.2 MPa. Moreover, the in-plane λ (λ∥) and out-of-plane λ (λ⊥) at room temperature reached 16.83 W/(m·K) and 1.42 W/(m·K), respectively. Both theoretical simulations and experiments demonstrated that the positive effect was due to the strong interaction between the electron-deficient imide ring in PI macromolecules and the electro-negative F atom in the PFAL shell. Overall, this study provides a promising strategy for enhancing the interfacial interaction between metallic fillers and polymers for the development of high-performance flexible electronic devices.