Preparation of functionalized graphene by simultaneous reduction and surface modification and its polymethyl methacrylate composites through latex technology and melt blending

Graphene is a kind of very promising filler for polymer composites, but its irreversible aggregation when introduced into polymers is a challenge for property enhancements and limits its industrial application. To address this, we report one-step covalent functionalization and simultaneous reduction of graphite oxide (GO) with hydroxyethyl acrylate (HEA), resulting in a functionalized graphene with double bonds. The functionalized graphene obtained, noted as FGN, is successfully incorporated into polymethyl methacrylate (PMMA) matrix by latex technology and melt blending. Latex technology is used for the pretreatment of FGN through emulsion copolymerization between methyl methacrylate (MMA) monomers and FGN double bonds. After pretreatment of FGN, covalent attachment of PMMA particles to the edges of FGN sheets can effectively prevent their agglomeration and markedly improve their dispersion in the polymer matrix. Since these PMMA particles act as good compatibilizers in the interface between FGN and PMMA matrix during the melt mixing process, the PMMA/FGN composites obtained exhibit exfoliated morphology and very good dispersion, as evinced by the results from X-ray diffraction (XRD) and transmission electron microscopy (TEM). When even a small amount of FGN (<= 1.0 wt%) is incorporated, the thermal properties and mechanical properties of PMMA/FGN composites are enhanced significantly. The glass transition temperature (T-g) increases from 103.8 to 110.5 degrees C, while the tensile strength increases by 31.0% (1.0 wt% FGN addition). Moreover, the storage modulus of PMMA/FGN composites increases by 27% (1.0 wt% FGN addition) at room temperature. These enhancements are attributed to the strong chemical interaction between the FGN sheets and PMMA and the good distribution of FGN sheets in the PMMA matrix. (C) 2013 Elsevier B.V. All rights reserved.