Anisotropic high-strength polyimide-based electromagnetic interference shielding foam based on cation-π interaction

Effective electromagnetic interference (EMI) shielding plays a vital role in numerous applications by mitigating the detrimental impacts of electromagnetic waves. In this study, we developed a novel anisotropic MXene@PI hybrid foam for efficient EMI shielding using a synergistic approach involving directional freezing, freeze-drying, thermal imidization, and a subsequent dip-coating step. The cation-π interaction was harnessed to create a crosslinked structure for enhancing the mechanical properties of the polyimide (PI) foam and also to improve the interfacial interaction between MXene and the inner wall of the foam. The foam exhibited a tubular structure in a vertical frozen direction while adopting a honeycomb-like structure in a parallel freezing direction. The anisotropic MXene@PI-5 hybrid foam demonstrated remarkable EMI shielding effectiveness of up to 62.7 dB in the vertical freezing direction, 158.02 % higher than that observed in the parallel direction, and 109.70 % higher than that in the isotropic foam with the same loading of MXene. This anisotropic MXene@PI hybrid foam offers great potential for applications requiring efficient EMI shielding, such as aerospace, electronics, telecommunications, etc. The unique combination of the cation-π interaction and anisotropic structure provides enhanced EMI shielding properties, making it a promising candidate for future EMI shielding materials.