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Here, Ni@graphene nanoplatelet (GNP) nanohybrids are obtained via an interfacial reaction growth method and a series of poly(methyl methacrylate) (PMMA)/Ni@GNP composites are prepared by a solution mixing‐ultrasonic dispersion‐hot pressing technology. The influence of Ni@GNP on the electromagnetic interference (EMI) shielding, dielectric, and thermal management behaviors of the composites is intensively investigated. The microcapacitors formed using Ni@GNP as plates and PMMA as matrix significantly improve the dielectric properties of the composites. Enhancement on thermal conduction and EMI properties of PMMA composites with increasing Ni@GNP content can be ascribed to the unique structure of Ni@GNP and it is the filler interconnection network that renders the composite's desirable thermally conductive and thermomechanical properties. A facile way of fabricating polymeric composites with satisfactory thermal conductivity and high‐performance electromagnetic shielding is provided here. The obtained polymer composites display highly promising applications in the thermal management and EMI shielding of electronic devices. [ABSTRACT FROM AUTHOR]

In this work, graphene nanoplatelet (GNP) filled polymethyl methacrylate (PMMA) composites were prepared using solution method via a specially designed route and relatively high thermal conductivities of the composites were achieved at a low GNP loading. The effect of GNP content on rheological behavior, thermal and electrical conductivity of the composites was intensively investigated. Thermorheological complexity was displayed at elevated GNP loading, and the rheological percolation threshold of GNP in PMMA decreased from 7.96 wt% at 220 °C to 4.02 wt% at 260 °C according to Winter - Chambon method, suggesting that GNP was more likely to form a seepage network at higher temperature. The DMTA results showed that the increase in moduli of the composites should be ascribed to the formation of the GNP-GNP network structure. The electrical conductivity of the composites underwent a sudden jump by seven orders of magnitude, which also indicated the formation of a GNP conductive pathway in the matrix with an electrical percolation threshold of 2–4 wt%. The results of transient temperature measurement were in good consistent with the thermal conductivity versus GNP loading, which was compared with various thermal conduction models with a modified Agari model presenting an acceptable evaluation of the dispersion status of GNP in the matrix. The experimental electrical and thermal conductivities as a function of GNP content could well be interpreted by the filler network structure as observed in morphological studies. • Thermorheological complexity displayed at elevated GNP loadings. • Temperature dependence of rheological percolation threshold of GNP in PMMA. • Electrical percolation threshold of GNP in PMMA within concentration of 2–4 wt%. • Thermal conductivity versus GNP loading reasonably predicted by a modified Agari model. • Relatively high thermal conductivities of composites achieved at low GNP loadings. [ABSTRACT FROM AUTHOR]