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An intercalation polymerization is applied to regulate the hybridizing structures of polyaniline@graphene (PANI@GE). Polarization of GE sheets is realized, which is attributed to the hybridization by the in situ intercalation-polymerized PANI molecules. The polarizing effect on GE is confirmed by characterizations and density functional theory calculations, and the results indicate that distinct p−π and π–π interactions exist between the PANI molecules and the GE sheets. As a result, this new structural hybrid leads to a high performance of microwave absorption. The minimum reflection loss (RL) of the optimized PANI@GE hybrid can be as low as −64.3 dB at 10.1 GHz with the RL bandwidth of −10 dB being 5.1 GHz (from 8.6 to 13.7 GHz). A further study reveals a special mechanism for the electromagnetic energy consumptions by the structural resonance of the polarized GE-based hybrids, a complex macromolecule. In addition, the fully separated GE provides a good impedance matching, together with the widely held multiscaled relaxations of the interfacial polarization.

Abstract:The rapid development of society has promoted increasing demand for various polymer materials. A large variety of efforts have been applied in order for graphene strengthened polymer composites to satisfy different requirements. Graphene/polymer composites synthesized by traditional strategies display some striking defects, like weak interfacial interaction and agglomeration of graphene, leading to poor improvement in performance. Furthermore, the creation of pre-prepared graphene while being necessary always involves troublesome processes. Among the various preparation strategies, an appealing approach relies on intercalation and polymerization in the interlayer of graphite and has attracted researchers' attention due to its reliable, fast and simple synthesis. In this review, we introduce an intercalation polymerization strategy to graphene/polymer composites by the intercalation of molecules/ions into graphite interlayers, as well as subsequent polymerization. The key point for regulating intercalation polymerization is tuning the structure of graphite and intercalants for better interaction. Potential applications of the resulting graphene/polymer composites, including electrical conductivity, electromagnetic absorption, mechanical properties and thermal conductivity, are also reviewed. Furthermore, the shortcomings, challenges and prospects of intercalation polymerization are discussed, which will be helpful to researchers working in related fields.

Rational design on the components and microstructures of microwave-absorbing materials can pave the way for upgrading their performances in electromagnetic pollution prevention. In this study, Fe3O4–graphite intercalation hybrids (Fe3O4-GIH) with unique sandwich-like microstructure are fabricated by a molten salt route and subsequent temperature reduction. It is found that the gaseous FeCl3 molecules at high temperature can diffuse into the graphite interlayer plane to obtain FeCl3-GIH, and the intercalated FeCl3 is then transferred into Fe3O4 nanoparticles under high temperature reduction, which can prop open the graphite interlayer, thus achieving sandwich-like Fe3O4-GIH. Therefore, one-step synthesis can give perfect features, such as transformation of graphite into graphene sheets, introduction of a magnetic component, and construction of multiple interfaces, which are a benefit to the microwave absorption (MA). As a result, the maximum reflection loss of the as-obtained Fe3O4-GIH can be up to −51 dB at 4.3 GHz with a matching thickness of 4.8 mm. Furthermore, the MA performances can be tuned by regulating the interlayer spacing of Fe3O4-GIH. The excellent microwave absorption performance may attribute to the synergistic effect between Fe3O4 nanoparticles with magnetic loss, graphite with dielectric loss, and novel interfacial polarization originating from the sandwich-like Fe3O4-GIH. Additionally, it can be supposed that these sandwich structures are more beneficial for scattering the incident electromagnetic wave due to their large spacing and porous features.

Development of high-performance materials for electromagnetic wave absorption has attracted extensive interest, but it still remains a huge challenge especially in reducing density and lowering filler loading. Herein, a hierarchical all-carbon nanostructure is rationally designed as follows: the defect-rich hollow graphite capsules (GCs) controlled by the size/density of ZnO templates are synthesized on the surface of helical carbon nanotubes (HCNTs) to form a hybrid nanocomposite, denoted as GCs@HCNTs. As a result, the GCs@HCNTs demonstrate a strong and wide absorption performance with a very low filler loading of 10 wt %. The minimum reflection loss reaches −51.7 dB at 7.6 GHz, and the effective bandwidth (below −10 dB) ranges from 8 to 14 GHz, covering the whole X or Ku bands. The hierarchical nanostructure and homoatomic heterogeneous interface are beneficial to impedance matching and bring additional dipole polarization enhanced by the structural defects, which may enlighten the design of ultralight and broadband high-performance electromagnetic wave absorption materials.