Investigating the preparation routes to aqueous graphene dispersions and their influence on electrical conductivity of polymer composites

Graphene was produced from graphite powder using the three best known water-based conversion approaches. The first two are based on chemical oxidation methods, only differing in the reduction process, either by the use of hydrazine or by thermal expansion, respectively. The third one is based on long-term ultrasonic exfoliation. Water/surfactant solutions were prepared with these three nanofillers and latex technology was applied for the preparation of conductive graphene/polystyrene composites, with well-dispersed graphene platelets. Microscopic studies showed that both reduction processes lead to agglomeration/wrinkling of the nanoplatelets, even though they yield composites with high conductivity and low percolation threshold. Although mechanical ultrasound exfoliation of graphite produces less defective multi-layer graphene, these platelets have a smaller lateral size and their composites exhibit a higher percolation threshold.