Gravity-driven self-assembly of thickness-direction asymmetric TA@MXene/WPU composite films for high-performance electromagnetic interference shielding

With the rapid development of flexible electronics and wireless communication technologies, lightweight and flexible electromagnetic interference (EMI) shielding materials are in high demand. However, conventional homogeneous MXene/polymer composites often exhibit excessive surface reflection and insufficient internal electromagnetic attenuation. In this work, a tannic acid-modified MXene (TA@MXene)/waterborne polyurethane (WPU) composite film with a thickness-direction asymmetric structure was fabricated through a solution-casting process combining gravity-driven sedimentation and solvent evaporation. TA modification improved the dispersion stability of MXene nanosheets and facilitated the formation of an asymmetric conductive structure within the WPU matrix. The resulting composite film exhibited anisotropic electrical conductivity and effective EMI shielding performance in the X-band. At a TA@MXene loading of 12.5 wt%, the film achieved an EMI shielding effectiveness of 34.3 dB and an SSE/t value of 4975 dB cm 2 g −1 . In addition, the composite film maintained good mechanical flexibility, tensile strength, and improved flame-retardant performance. This work demonstrates an effective strategy for constructing multifunctional MXene-based flexible shielding materials through spatial regulation of conductive networks.