Multifunctional Ti3C2Tx-(Fe3O4/polyimide) composite films with Janus structure for outstanding electromagnetic interference shielding and superior visual thermal management

Flexible multifunctional polymer-based electromagnetic interference (EMI) shielding composite films have important application values in the fields of 5G communication technology, wearable electronic devices and artificial intelligence. In this work, Fe 3 O 4 /polyamic acid (PAA) nanofiber films are prepared by in-situ polymerization and electrospinning technology, and Ti 3 C 2 T x nanosheets are deposited on the surface of the Fe 3 O 4 /PAA nanofiber films via vacuum-assisted filtration. Then, Janus Ti 3 C 2 T x -(Fe 3 O 4 /polyimide (PI)) composite films are obtained by thermal imidization. The two sides of the Janus films exhibit completely different properties. The Fe 3 O 4 /PI side has excellent hydrophobicity and insulation property, and the Ti 3 C 2 T x side has hydrophilicity and terrific conductivity. When the mass fraction of Ti 3 C 2 T x is 80 wt.%, the Janus Ti 3 C 2 T x -(Fe 3 O 4 /PI) composite film has excellent EMI shielding performances and mechanical properties, with EMI shielding effectiveness, tensile strength and Young’s modulus reaching 66 dB, 114.5 MPa and 5.8 GPa, respectively. At the same time, electromagnetic waves show different absorption shielding effectiveness (SE A ) when incident from two sides of the Janus films. When the electromagnetic waves are incident from the Fe 3 O 4 /PI side, the SE A of the Janus film is 58 dB, much higher than that when the electromagnetic waves are incident from the Ti 3 C 2 T x side (39 dB). In addition, the Ti 3 C 2 T x side of the Janus Ti 3 C 2 T x -(Fe 3 O 4 /PI) composite films also has excellent electrothermal and photothermal conversion performances. When the applied voltage is 4 V, the stable surface temperature reaches 108 °C; when it is irradiated by simulated sunlight with power density of 200 mW/cm 2 , the stable surface temperature reaches 95 °C.