A preparation process of PMMA/graphite nanocomposites was developed via in situ polymerization of monomers in the presence of sonicated expanded graphite with the aid of sonication.Expanded graphite was sonicated in a 70% aqueous alcohol solution to get graphite platelets (NanoG) with thickness of 30～80 nm and diameter of 0.5～20 μm.The NanoG were dispersed in MMA monomers with BPO initiator.In situ polymerization was taken place when the mixture was heated under sonication.The TEM studies showed that the graphite nano-platelets were well dispersed in the PMMA matrix.Solution cast films of the nanocomposite were used for electrical conductivity measurements.The percolation threshold of polymer/NanoG nanocomposite films at room temperature was lower than 1.0 wt%,which was much lower than that of the composites with conventional graphite filler which was 5.5 wt%.The electrical conductivity reached 10 -3 S/cm at a graphite content of about 4.0 wt%.The special structure of graphite nano- platelets with high aspect ratio of as high as 100～500 (width-to-thickness) played an important role in forming a conducting network within the PMMA matrix.
