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The strong influence of graphite oxide (GO) nanofiller on the glass transition temperature ( T g ) of epoxy resins, generally attributed to restricted molecular mobility of the epoxy matrix by the nanofiller or to the crosslinking of GO layers via the epoxy chains, is investigated. The study confirms that large increases of the glass transition temperature of the nanocomposite can be observed in presence of GO. However, similar T g increases are observed, when the filler is a high-surface-area graphite (HSAG), lacking oxidized groups. Moreover, these T g differences tend to disappear as a consequence of aging or thermal annealing. These results suggest that the observed T g increases are mainly due to a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and di-amine), rather than to reaction of the epoxide groups with functional groups of GO. This hypothesis is supported by investigating the catalytic activity of graphite-based materials on reactions between analogous monofunctional epoxide and amine compounds. [ABSTRACT FROM AUTHOR]

Robust monolithic aerogels based on syndiotactic polystyrene (s-PS) and graphene oxide (GO), and exhibiting high surface areas (240-290m²/g) and low density (0.02-0.2g/cm³), are presented. These aerogels are obtained by supercritical carbon dioxide extraction of s-PS/GO gels, which were prepared by s-PS dissolution in GO dispersions in suitable organic solvents. In contrast to other GO-based aerogels, the s-PS/GO aerogels are blue, not black. This blue color is due to Rayleigh scattering by isolated particles of reduced graphene oxide, whose thickness is much smaller than the wavelength of the light. The s-PS/GO aerogels exhibit the functionalities of the nanoporous-crystalline &#948 form of the polymer and of reduced and structurally uncorrelated GO layers and maintain the ductility of pure polymer aerogels. Uses can be anticipated as supported GO-based catalyst or "masterbatches" for GO rich nanocomposites. [ABSTRACT FROM AUTHOR]

Abstract: Graphite oxide intercalation compounds (GOIC), exhibiting a large distance between graphite oxide sheets as well as a long-range order in the organization of guest species, are obtained by intercalation of organic cations containing two long hydrocarbon tails. In particular, graphite oxide layers with interlayer spacing of 0.84nm, when ionically bonded with cations with two C18 chains, lead to GOIC with interlayer spacing of 3.4nm and with a hexagonal rotator order in the packing of the long hydrocarbon tails. The intercalation of a second guest species with one or two long hydrocarbon tails not only leads to a further large increase of the interlayer spacing (from 3.4nm up to 5.8nm, for guests with C18 alkyl chains) but also, surprisingly, improves the order in the stacking of the layers as well as in the organization of the hydrocarbon chains in the interlayer space. X-ray diffraction measurements on powders and oriented films indicate that these ordered GOIC present intercalate structures with inclined and perpendicular bilayers of guest molecules. Differential scanning calorimetry associated with X-ray diffraction measurements show the occurrence of reversible loss of the hydrocarbon rotator order, which can be associated with significant changes of the interlayer spacing. [Copyright &y& Elsevier]