Nanocomposites of poly(methyl methacrylate)/reduced graphene oxide (PMMA/rGO) without and with decorated magnetite nanoparticles with a segregated structure were prepared using emulsifier-free emulsion polymerization. Various characterization techniques were employed to validate the presence of the nanofillers and the formation of the segregated structure within the nanocomposites. The percolation threshold of the nanocomposites was found to be 0.3 vol %, while a maximum electrical conductivity of 91.2 S·m and electromagnetic interference shielding effectiveness (EMI SE) of 63.2 dB (2.9 mm thickness) were achieved for the PMMA/rGO nanocomposites at a loading of 2.6 vol % rGO. It was also observed that decorating rGO with magnetite nanoparticles (hybrid nanocomposites) led to a tremendous increase in EMI SE. For instance, 1.1 vol % PMMA/rGO nanocomposites indicated an EMI SE of 20.7 dB, while adding 0.5 vol % magnetite nanoparticles enhanced EMI SE to 29.3 dB. The excellent electrical properties obtained for these nanocomposites were ascribed to both superiorities of the segregated conductive structure and magnetic properties of the magnetite nanoparticles.

with a large specific surface area featuring both hydrophilic and hydrophobic characters. [4] The hydrophobic nature of GO nanosheets originates from the basal plane, i.e., carbon rings, while hydrophilicity is imparted to GO by the surface and edge functional groups, e.g., hydroxyl, carboxylic, and epoxy groups. Due to this dual nature, GO nanosheets self-assemble at oil/water (O/W) interfaces, forming nanometer-thick barriers separating water and oil. Thus, by tuning the carbon to oxygen ratio, GO can be assembled at liquid-liquid interfaces to generate hierarchical structures with defined functionalities. [5,6] The promise of GO for numerous applications has increased interest in its interfacial behavior.The assembly of GO at liquid-liquid interfaces has been investigated primarily by dynamic interfacial tension (IFT). Previously, we [7] showed that GO assembles at the O/W interfaces, forming, predominantly a tessellated, nanosheet barrier reducing the interfacial surface energy between the liquids. The low bending modulus of GO enables the assemblies to conform to the curvature of the interface. Similarly, Kim et al. [1] investigated the activity of GO nanosheets at air-liquid, liquid-liquid, and liquid-solid interfaces, showing that, despite the stable dispersion of GO in water, GO segregates to the interfaces to reduce the interfacial tension. Imperiali et al. [8] reported on GO film formation at air/W interfaces, performing compression/expansion experiments in a Langmuir trough. They found that GO assembles at the surface and, upon compression, maitains a single layer thickness, resisting overlap due to attractive lateral forces. However, the influence of GO on the viscoelastic properties of the O/W interfaces has not been thoroughly investigated, which is critical for applications, including emulsification, enhanced oil recovery (EOR), and all-liquid 2D and 3D printing. We recently demonstrated, for example, the importance of the interfacial rheology of O/W on the stabilization of Pickering emulsions. [9] It was shown that the interfacial rheology plays a decisive role in emulsion formation, [9,10] controlling the emulsion morphology and stability. [11,12] In all-liquid 3D printing, reducing the interfacial tension to retard Plateau Rayleigh (PR) instabilities and stabilize the interface [13] is essential. Several nanomaterials have been recently proposed for sculpting liquids. [14] For instance, the printability Tailoring the oil/water (O/W) interface is a prerequisite for structuring these two immiscible liquids into prescribed architectures, i.e., liquid-in-liquid printing, which is an emerging area in material science. Here, assemblies of graphene oxide (GO) at O/W and air/W interfaces are characterized using a wide range of interfacial rheological techniques. It is shown that the GO nanosheets assemble at the interface, even at extremely low concentrations as low as 0.04 vol%, significantly increasing the elasticity at O/W or air/W interfaces. This is attributed to the combined hydrophobic and hydrop...

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