Graphene, monolayer of carbon atoms arranged in a honeycomb network, has recently gained revolutionary aspirations (Novoselov et al., 2005; Novoselov et al., 2007; Heersche et al., 2007; Zhang (a) et al., 2005; Stankovich et al., 2006) because of its remarkable electronic properties (Zhang (b) et al., 2005; Berger et al., 2004), unusual thermal properties (Balandin et al., 2008) and good mechanical properties (Lee et al., 2008). These extraordinary properties make it an excellent choice as inorganic fillers to substantially improve electrical, thermal and mechanical properties of composite materials (Stankovich et al., 2006; Ramanathan et al., 2008). Several effective techniques have been developed for preparing graphene nanosheets, including chemical (Stankovich et al., 2006) and mechanical exfoliation (Novoselov et al., 2004), alkali metals intercalation and expansion (Viculis et al., 2003), microwave chemical vapor deposition (Wang et al., 2009), substrate-based thermal decomposition (Berger et al., 2004), and thermal exfoliation of graphite oxide (GO) (McAllister et al., 2007). Among them, chemical reduction of exfoliated graphite oxide in the presence of a surfactant or polymer is a relatively new method to prepare electrically conductive individual graphene sheets. Stankovich (Stankovich et al., 2006) put forward a new process to produce polystyrene/graphene nanocomposites via ultrasonic exfoliation and chemical reduction of graphite oxide and molecular-level dispersion of chemically modified graphene nanosheets. In addition, the thermal exfoliation and in situ reduction method can conveniently produce graphene nanosheets for mass production. As confirmed by Aksay and co-workers (McAllister et al., 2007), in situ reduction reaction took place during the thermal exfoliation process, which converted insulating graphite oxide to conducting graphene. More importantly, the graphene resulted through thermal exfoliation still contained some oxygen-containing groups. The oxygen functionalities on the graphene nanosheets will facilitate their dispersion in polar polymers (Ramanathan et al., 2008). Effective medium approximation indicated that graphene is more effective in improving conductivity of composites than carbon nanotubes (Xie et al., 2008). The polystyrene/graphene nanocomposites prepared by chemical modification and reduction in