Multifunctional polyimide/boron nitride nanosheet/Ti3C2Tx MXene composite film with three-dimensional conductive network for integrated thermal conductive, electromagnetic interference shielding, and Joule heating performances

With the demand for further miniaturization and higher frequency operation of electronic devices, polymer films with high thermal conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) are urgently required. Herein, polyimide (PI)/boron nitride nanosheets (BNNS) aerogels with oriented porous structure are fabricated by unidirectional-freezing and freeze-drying methods. Subsequently, hierarchical PI/BNNS/Ti3C2Tx composite films with consecutively electrically and thermally conductive networks are successfully prepared via a unidirectional PI/BNNS aerogels-assisted immersion and hot-pressing strategy. Owing to the three-dimensional conductive dual networks of BNNS and Ti3C2Tx, the composite film exhibits excellent thermal conductivity with the maximum in-plane value of 4.73 W/(m·K), increased by 456% compared to pure PI film. Moreover, the conductive network of Ti3C2Tx is conducive to the excellent EMI shielding performance, endowing the PI/BNNS/Ti3C2Tx composite film with an outstanding EMI SE value of 49.2 dB at 8.2 GHz with a low MXene content of 6 wt% and thickness of 300 μm. Furthermore, the composite film shows the superior Joule heating performance with fast thermal response and sufficient reliability. Therefore, the resulting composite film exhibits excellent thermal conductive, EMI shielding and Joule heating performance, which enables the potential application of multifunctional composites for thermal management and EMI shielding.