Electrically Conductive Graphene/Poly(methyl methacrylate) Composites with Ultra‐Low Percolation Threshold by Electrostatic Self‐Assembly in Aqueous Medium

Thermally reduced graphene modified with cationic ammonium ions (AAG)—affording a stable dispersion in water—self‐assembles well by electrostatic interaction on the surface of anionic poly(methyl methacrylate) (PMMA) particles of various sizes, by simple mixing in water. An interconnected 3D electrically conductive network of AAG is effectively generated in the composite when the self‐assembled composite is compression molded. The AAG network becomes wide‐meshed and electrical conduction is improved when the PMMA particle size increases, exhibiting a percolation threshold of electrical conductivity as low as 0.06 vol%. In contrast, the protection of PMMA from oxidation by air is more effective when the network is fine‐meshed.