We herein report on the preparation of epoxy nanocomposites, which had enhanced thermal conductivities but were still electrical insulators, incorporating hybrid nanosheets (NSs) with sandwich structures composed of thermally reduced graphene oxide (TRGO) and silica. The silica layer covered the surface of the TRGO, hindering electrical conduction and effectively forming a 3D phonon transport channel that had a unique effect on the electrical and thermal properties of the epoxy matrix. A 1 wt% TRGO-silica NS epoxy nanocomposite maintained an electrical resistivity of 2.96 × 10(11)Ω cm, and its thermal conductivity was 0.322 W m(-1) K(-1), which is 61% higher than the conductivity of an epoxy nanocomposite without TRGO-silica NSs (0.2 W m(-1) K(-1)).

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We describe the preparation of vinyl-terminated benzoxazine-functionalized graphene using free radical grafting. The resulting functionalized graphene (f-graphene) was incorporated into bis(3-allyl-3,4-dihydro-2H-1,3-benzoxazinyl)methane (V-BF-a) monomer in order that nanocomposites could be prepared. Results of scanning electron microscopy and transmission electron microscopy revealed that the sheets of f-graphene were well dispersed throughout the matrix, and there was a strong interfacial interaction between the f-graphene and polyV-BF-a. The inclusion of f-graphene into the nanocomposites resulted in a material with a high thermal stability and a low coefficient of thermal expansion (CTE); increasing the content of f-graphene reduced the CTE significantly more. A reduction in the CTE of up to 48% was produced by adding just 1 wt% of f-graphene; this corresponded to an increase of 12 • C in the glass transition temperature. These results suggest that f-graphene nanocomposites can be 'tuned' to give materials with both a low CTE and a high thermal stability, and that graphene composites of this type can thus be manufactured to withstand a wider range of temperatures.

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