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Page 4 of 25 Liu et al. Soft Sci. 2025, 5, 7 https://dx.doi.org/10.20517/ss.2024.69

[27]
The structure design is an appropriate way to enhance EMW absorption capabilities . It is based on the
dispersive spatial distribution of nanoparticles, multiple scattering loss for the hierarchical structure, and
[47]
interfacial polarization for large heterogeneous surfaces . Reasonable microstructures with multiple
heterointerfaces can change the complex permittivity. In addition, the internal voids can generate multi-
reflections and scatterings, enhancing the impedance matching and ability to attenuate EMW . Porous
[17]
structures, multilayer structures, segregated structures, core-shell structures, hydrogel, aerogel, prefabricated
conductive structures, etc., were designed in conductive polymer composites (CPCs) to achieve high-
efficiency microwave shielding [48,49] .

Multi-component composites
Because of their special characteristics and single loss mechanism, single-component systems can rarely
achieve appropriate impedance matching and high absorption effectiveness [7,50-53] . As a result, creating multi-
component composites using materials such as carbon and conductive polymers can overcome the problem
of high filling loading while also achieving synergistic effects between the components [27,54] .

By introducing a second or third component phase, EMW absorbing materials can provide sufficient
heterointerfaces, abundant interfacial polarization, dielectric loss, and suitable impedance matching, thus
enabling efficient EMW absorption [55,56] . Owing to the variable charge distribution at the junction of two
areas with different dielectric characteristics, the Maxwell-Wagner-Sillars effect is produced in a
heterostructure. Meanwhile, a local dipole electric field will be formed by the capacitor-like interfaces; thus,
the combined motions of interfacial dipoles enhance the response with EMW and EMW attenuation [57-59] .

Porous structure
Based on Maxwell-Garnett theory, internal multiple scattering, impedance matching, and the dielectric
constant may all be enhanced by the porous structure with heterointerfaces [29,57,60,61] . Specifically, because
foaming concentrates conductive fillers in the cell walls and reduces the electrical threshold, porous CPCs
need less filler to create conductive networks than compact CPCs [10,34] . Meanwhile, the voids can produce a
large number of solid/air interfaces and adjust the impedance matching. By enhancing interfacial
polarization, reducing conductivity close to the polymer-gas interfaces, and prolonging the shielding/
absorption propagation path, these interfaces offer extra EMW shielding/absorption capabilities [9,62] .
Therefore, balancing conduction loss, polarization loss, impedance matching, and attenuation capability is a
potential advancement in heterogeneous porous CPCs [29,37,63] .

In-situ polymerization, phase inversion, supercritical CO foaming, freeze drying, 3D printing, and
2
thermally induced phase separation are some methods that can be successfully used to create porous
polymer-based EMW absorption materials .
[34]

Multilayered structure
The multifunctional demands are rarely met by CPCs with homogenous structures. For example, to satisfy
the requirements of infrared stealth and Joule heating, anisotropic thermal conductivity (TC) and electrical
conductivity are required. By creating continuous conductive networks and increasing multi-scattering, a
3D multilayered structure may increase EM absorption and realize infrared stealth by preventing heat
transfer [7,9,64] . Constructing a multilayered structure is a promising method to realize anisotropy. Fully
utilizing the advantages of single components to achieve the applicability of multiple functions is a perfect
approach to achieving anisotropy .
[15]