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Liu et al. Soft Sci. 2025, 5, 7 https://dx.doi.org/10.20517/ss.2024.69 Page 9 of 25

[44]
polymerization degree . It can further increase its EMW absorption capability by efficiently increasing the
[63]
interfacial polarization and conduction loss . Because of the impedance matching and heterostructures of
Fe O @PPy (FP), the composite at 2.08 mm had an EABmax of 6.00 GHz (12.0-18.0 GHz). Heterostructure
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provided the polarization fields and conduction and magnetic loss, and the PPy shell afforded dielectric
loss .
[47]
The hydrothermal reaction, in situ polymerization, freeze-drying, and reduction were used to prepare a FP
microsphere decorated reduced GO (rGO) [Figure 4A]. FP consumed EMW by dielectric and magnetic
losses. RGO functioned as a multi-reflection layer and formed conductive networks. FP and rGO improved
the impedance matching. The composite achieved an EAB of 5.26 GHz at 1.71 mm and an RLmin of
-61.20 dB at 1.89 mm . C-coated FeCoNi (FeCoNi@C) spatially confined within hollow carbon nanoboxes
[44]
(HCNB) were prepared using core-shell FeCoNi Prussian blue analogs (PBAs)@PPy as precursors. Because
of the differences in thermal stability of PPy and FeCoNi PBAs, the derivative had a yolk-shell structure if
the inward contraction of the core caused by heat was greater than the interface contact; otherwise, it had a
hollow structure. The yolk-shell sample had an EABmax of 5.8 GHz and an RLmin of -52.4 dB, which
results from the synergism of dielectric and magnetic losses, and the superior impedance matching
[Figure 4B] . ZnFe O @PPy microspheres were prepared using pyrolysis and in situ polymerization
[23]
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[Figure 4C]. The core-shell structure of ZnFe O @PPy optimized the impedance matching, with an RLmin
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of -41 dB and an EBA of 4.1 GHz. The polarization from the heterointerfaces by the wrinkle structure,
combined with the conductivity of PPy leading to conduction loss, jointly contributed to the increased
dielectric loss . NiFe O /PPy composites with negative permittivity were prepared by surface-initiated
[8]
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2
polymerization. The RLmin of -40.8 dB was observed in the composite with 40.0 wt% of NiFe O /PPy at
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1.9 mm. The EAB reached 6.08 at 2.08 GHz, which was attributed to improved independence matching and
the synergism of conduction loss, magnetic loss and dielectric loss .
[11]
A PPy/CaCu Ti O /CoFe O was prepared via in-situ chemical oxidative polymerization. A bowl-like
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12
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structure was formed because of the interfacial interactions of PPy and nanofillers. The periphery of the cup
consisted of CaCu Ti O and CoFe O . The composite had an EMI SE of 30 dB, with the combined
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12
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magnetic and dielectric losses, losses from free charges in the interface, interfacial polarization, and the
[40]
wedge effect responsible for the absorption-dominated mechanism [Figure 5A] . A PPy@Co/CoFe O 4
2
@hollow bowl-like C (PPy@Co/CoFe O @HNBC) was prepared. PPy and Co/CoFe O were added via in-
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2
2
4
situ growth and polymerization after HNBC was created using a template approach. The composite at
1.90 mm had an RLmin of -61.85 dB at 12.80 GHz and an EAB of 5.60 GHz at 1.70 mm, which was
attributed to its distinct structure and the combined effects of natural and exchange resonance-induced
[63]
magnetic loss, conduction and polarization-induced dielectric loss [Figure 5B] .
A conductive MOF Cu (HHTP) (hexahydroxytriphenylene, HHTP) was packed on the PPy by
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hydrothermal polymerization. MOFs improved interfacial polarization, conductive loss and impedance
matching, which benefited EM absorption. The EAB of the material can reach 6.68 GHz (11.00-17.68 GHz).
The RLmin and EAB of the composite at 2.7 mm reached -59.34 dB and 6.42 GHz . MXene was loaded
[13]
with co-substituted beta(2)-Keggin-type polyoxometalate doped PPy and Fe O . As a proton acid doped
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PPy, polyoxometalate and HCl could adjust the impedance matching and conductivity. Fe O caused
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multiple polarization and magnetic loss; dipoles, defects, and dangling bonds caused dipole polarization;
and the charge accumulated at the interface caused interfacial polarization. The composite at 1.7 mm with
45 wt% filling had an RLmin and EAB of -62.6 dB and 9 GHz .
[72]