The polymer itself has low electrical conductivity, necessitating the continuous addition of conductive fillers to the polymer matrix to impart conductivity. However, excessively high filler content increases costs and processing difficulty, and damages the material’s mechanical properties [140,141,142]. These challenges are effectively addressed by creating polymer-based EMI shielding materials with segregated structures. The isolation structure of these materials ensures that conductive fillers are distributed only between the polymer particle interfaces, preventing them from dispersing freely throughout the matrix. This restricted distribution increases the probability of filler overlap at the interfaces and significantly reduces the percolation threshold. Consequently, even at low filler content, the composite material exhibits strong electrical conductivity and EMI shielding capability [143,144,145]. Research by numerous investigators has demonstrated that the generation of a segregated structure is advantageous for reducing the percolation threshold of the composite, while synergistic filler interactions enhance the material’s shielding ability and mechanical properties [39,40,146,147,148,149]. The recent studies of segregated-structured electromagnetic shielding materials are summarized in Table 3. Zhang et al. [150] prepared PVDF/Fe₃O₄-RGC composite using layered electrostatic assembly and hot pressing. Wu et al. [151] obtained Fe₃O₄@PA6/MWCNT composite with layer-adding manufacturing and molding. They found that establishing a separation structure could form a complete conductive network, and adjusting the content of magnetic fillers could effectively improve the EMI SE of the composite. Yang et al. [152] obtained TPU/EG(expanded graphite)/AG(silver) composite material. The inclusion of the Ag component at just 0.58 vol% led to remarkable improvements in the syntactic foam’s conductivity and EMI SE, reaching 171.2 S/m and 56.3 dB, respectively—well exceeding the minimum requirements for commercial EMI shielding. The introduction of a porous structure effectively mitigates the impedance mismatch between the surrounding air and the composite material, facilitating more incident electromagnetic waves and reducing reflectivity. The material’s reflection efficiency in the X-band decreased from 99% to 31%, successfully mitigating secondary electromagnetic wave emission pollution. Additionally, the strong interfacial bonding between the filler and matrix ensures excellent compressibility recovery and shielding stability, even after 50 compression cycles. Wang et al. [153].prepared BPEI(multiblock polyetherimide)/MLG(multilayer graphene) composites. Due to the existence of two blocks with large TG differences in BPEI, the polymer has a high chain mobility, which allows it to inter-diffuse between the BPEI particle interfaces below TK-N, forming a good isolated conductive network. The findings demonstrated that the BPEI/MLG composite loaded with 5.0 wt% MLG generated an isolation structure at a temperature of 270 °C, thereby giving it an electrical conductivity of 313.5 S/m and an EMI shielding performance of 62.2 dB. Ma et al. [154] prepared a CNT/PDMS(polydimethylsiloxane) composite by establishing chemical bonds between them. The cross-linked network of PDMS microspheres prevents the penetration of CNTs into the polymer microcells, resulting in the formation of segregated structures. The results showed that even with only 2.2 vol% of CNT, this composite exhibited exceptional shielding performance at 47.0 dB. Notably, the tensile strength and elongation at break of the composite material reached 3.6 MPa and 87.0%, respectively, marking a substantial increase of 35.0 and 7.0 times compared to traditional isolation composite materials. Additionally, the material exhibited excellent reliability, retaining a high EMI SE of 80% even after undergoing 1000 strain-release cycles at 30% ultimate elongation.

Materials with a segregated structure have garnered considerable interest due to their outstanding EMI shielding performance and remarkably low percolation threshold. However, the distribution of conductive fillers at the polymer particle interface poses challenges, hindering molecular chain diffusion and affecting interface compatibility. Additionally, agglomerated conductive fillers generate micropores along the direction of the conductive path. These adverse circumstances will impact the mechanical characteristics of the polymer-based EMI shielding material with a segregated structure [155,156,157,158]. Yang et al. [159] added SiO₂ particles to PDMS, and the EMI SE of the composite was improved due to the volume exclusion effect and multi-interface. However, nanoparticles disrupt conductive networks.

The polymer-based EMI shielding composite material with a layered structure contains multiple interfaces, allowing for repeated reflection of electromagnetic radiation, leading to polarization loss and electromagnetic wave absorption loss [160,161]. This layered structure of EMI shielding material can achieve high electromagnetic shielding performance even with a low content of conductive filler, while offering design flexibility. Typically, polymer-based electromagnetic shielding composites with a layered structure exhibit sandwich and gradient configurations, which can be easily prepared using methods like vacuum filtration and deposition [162,163,164]. Due to their strong absorbing ability, these layered materials find extensive applications in critical fields such as military technology and precision instruments, significantly reducing secondary pollution caused by electromagnetic wave reflection [165,166,167,168]. Yu et al. [169] prepared PI(polyimide)/Ti₃C₂Tx Mxene/AgNW(silver nanowire) composite through electrostatic spinning and a hot-press approach. Wu et al. [170] obtained PPA6@NiM(magnetic PA6 microspheres)/PDMS composite using the solvent coprecipitation method. Chu et al. [171] prepared h-PANI/CNF/Mxene composite films with the alternating vacuum-assisted filtration method. Guo et al. [172] obtained ANF(aramid nanofiber)/AgNW/GN composite films through a vacuum filtration and hot-press approach. They found that the electromagnetic shielding material with a layered structure exhibited a strong absorbing ability, primarily attributed to the formation of a dense conductive network in the core layer of the material and excellent adhesion between the layers [42,169,170,171,172]. Table 4 shows the recent research of layered-structured electromagnetic shielding materials. Song et al. [173] obtained TPU/MWCNT electromagnetic shielding material with a sandwich structure through the CO₂ foaming method.