Anisotropic EMI Shielding Performance of Unidirectionally Aligned Ti₃C₂Tₓ MXene/PDMS Composites

Two-dimensional Ti₃C₂Tₓ MXene has attracted considerable attention as a conductive filler for lightweight electromagnetic interference (EMI) shielding composites owing to its high electrical conductivity and layered structure. However, its susceptibility to oxidation and poor interfacial compatibility with hydrophobic polymers limit its practical application in polymer nanocomposites. In this study, MXene was synthesized from the Ti₃AlC₂ MAX phase using a modified HF/HCl etching method, followed by thermal treatment under an inert atmosphere to improve its compatibility with polydimethylsiloxane (PDMS). Subsequently, anisotropic MXene/PDMS composites were fabricated through unidirectional freeze casting followed by PDMS impregnation. The resulting composites possessed an aligned MXene network along the ice-growth direction, providing continuous conductive pathways. Despite the low MXene content of 1.53–2.59 wt%, the composites exhibited a high electrical conductivity of up to 45.5 S cm⁻¹ and an excellent EMI shielding effectiveness of up to 61.4 dB in the X-band. The thickness-normalized shielding effectiveness reached maximum values of 25.3 dB mm⁻¹ in the longitudinal direction and 18.5 dB mm⁻¹ in the transverse direction. In addition, the longitudinal composites showed higher permittivity than the transverse composites, indicating enhanced charge accumulation and interfacial polarization along the aligned MXene network. Reflection–transmission–absorption (R–T–A) coefficient analysis indicated a reflection-dominant shielding behavior in terms of the incident electromagnetic wave power, while the electromagnetic waves penetrating into the composites were effectively attenuated through ohmic loss, interfacial polarization, and internal scattering. This work presents an effective design strategy for lightweight, low-filler-content, and anisotropic MXene/PDMS composites for high-performance EMI shielding applications.