Poly(methyl methacrylate) nanocomposites based on graphene oxide: a comparative investigation of the effects of surface chemistry on properties and foaming behavior

The effects of oxygen functional groups and alkyl chains at the surface of graphene oxide (GO) on the thermal stability, mechanical properties and foaming behavior of poly(methyl methacrylate) (PMMA) nanocomposites were investigated. Alkyl-functionalized GO (GO-ODA) was prepared by grafting octadecylamine (ODA) on the surface of GO. PMMA/GO and PMMA/GO-ODA nanocomposite were obtained by solution blending and were foamed using supercritical carbon dioxide (scCO(2)). GO-ODA, with the presence of alkyl chains, showed a better dispersion capability in PMMA matrix than GO with a large amount of oxygen functional groups. In addition, the good dispersion capability increased thermal stability and mechanical strength. In comparison with PMMA/GO samples foamed at 70 degrees C, PMMA/GO-ODA nanocomposite foams displayed improved cell structures with higher cell density, smaller cell size and more homogeneous cell size distribution, which results from the strong heterogeneous nucleation due to alkyl chains on the GO surface. The foaming behaviors became more complicated at 80 degrees C as the GO might be intercalated and exfoliated with the aid of scCO(2), thus further enhancing the heterogeneous nucleation during the foaming process. The results indicated that the surface chemistry of GO was closely related to the properties and foaming behavior of the nanocomposites. (c) 2016 Society of Chemical Industry