Page 61 - Read Online

Page 10 of 34 Yan et al. Soft Sci. 2025, 5, 8 https://dx.doi.org/10.20517/ss.2024.66

intercalation and encapsulated them in polyurethane (PU) to fabricate highly efficient and durable EMI
[99]
shielding composites [Figure 3B] . Due to the EMW impedance mismatch caused by the high conductivity
of GNPs and the multiple reflection shielding mechanism inside PU, the composite material has a shielding
effect of up to 70.50 dB at a thickness of 2 mm. It is noteworthy that even after 500 cycles of mechanical
bending and two hours of immersion in pure water and ultrasonic treatment, the composite material’s
maximum EMI shielding effectiveness (SE) essentially stays the same, indicating the material’s EMI
shielding stability in harsh conditions. Furthermore, the composites have superior mechanical strength (1.4
times that of PU) and tensile mechanical characteristics (> 400%), opening up new possibilities for flexible
electronic gadgets of the future and aeronautical applications.

Similarly, CNTs, which possess excellent electrical properties, are commonly used to construct conductive
pathways in elastomeric matrices [100-102] . Chen et al. used quartz fiber cloth (QFC) reinforced multi-walled
CNTs (MWCNTs) to obtain carbon aerogel [QFC reinforced MWCNTs carbon aerogel (QMCA)], which
[103]
was then combined with PDMS to prepare a new flexible conductive composite (FCM) [Figure 3C] . The
high dielectric constant is caused by the polarization of the MWCNTs and the polymer matrix, which helps
achieve absorption-based shielding. In addition, the large number of nanotubes will build a denser
conductive network and reduce the interstitial distance of MWCNTs in the matrix, which makes the fiber
network rougher and improves the EMW conduction loss, thus allowing the composite to have a high EMI
shielding effect. Meanwhile, the flexible PDMS endowed the material with strong mechanical properties
(tensile strength and modulus of 129.6 MPa and 3.41 GP, respectively) and compressive strength. This
method maximized the advantages of both materials, significantly enhancing the mechanical and EMI
shielding performance of the composite, while also broadening the potential applications of the new flexible
conductive material. Even more praiseworthy is the work of Jia et al., who converted waste tire rubber
(GTR) combined with CNTs into a high-performance EMI shielding material with high value
[104]
[Figure 3D] . When combined with conductive CNTs, the inherent 3D crosslinking structure of GTR,
which is akin to that of high-viscosity gels, prevents CNTs from penetrating the interior of GTR and creates
a deviated structure that is selectively distributed at the interfaces of the structural domains of GTR. This
creates a high-density conductive network that improves the electrical and EMI shielding capabilities of the
polymer composites. Consequently, the composite material containing only 5.0 wt% CNTs has an EMI
shielding performance of 66.90 dB, much higher than the general commercial standard (20.00 dB).
Moreover, CNTs/GTR composites demonstrate excellent flexibility and stability, maintaining 93% of the
EMI SE after 5,000 cycles of repeated bending. Therefore, low-cost, high flexibility, and high EMI shielding
performance composite materials will shine in the next generation of flexible electronic products and
wearable flexible product applications.

If the highly conductive graphene and CNTs are combined, not only can the EMI energy be dissipated
through the conductive mismatch at the filler-matrix interface, but CNTs can also fill the gaps between
graphene sheets and form a conductive network by bridging the neighboring graphene to intertwine with
each other as a unique hierarchical structure, which can increase the propagation path of permeable EMI to
promote the interfacial polarization loss to attenuate EMI waves [105-108] . Lee et al. prepared epoxy-based
fabrics [polyester fabrics (PFs)] nanocomposites using single-walled CNTs (SWCNTs) combined with rGO
as conductive fillers [Figure 3E] . The effective dielectric loss at multiple interfaces in the SWCNTs/rGO
[109]
network, the enhanced dissipation of EMWs by the extended EM pathway, and the multi-scale porous
structure consisting of 3D micropores of the SWCNTs/rGO hybrids and macropores of the PF skeleton lead
to the increase in the impedance mismatch, interfacial polarization loss, and multiple scattering inside the
composites, which results in a higher shielding effect in the X-band, with higher SE (41.00 dB). Additionally,
PFs served as a flexible substrate, supporting the high dispersion of nanofillers in the polymer matrix,