Influence of Anionic Surfactants on the Fundamental Properties of Polymer/Reduced Graphene Oxide Nanocomposite Films

Surfactants are frequently employed in the fabrication of polymer/graphene-based nanocomposites via emulsion techniques. However, the impact of surfactants on the electrical and mechanical properties of such nanocomposite films remains to be explored. We have systematically studied the impact of two anionic surfactants [sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS)] on intrinsic properties of the nanocomposite films comprising reduced graphene oxide in a matrix of poly(styrene-stat-n-butyl acrylate). Using these ambient temperature film-forming systems, we fabricated films with different concentrations of the surfactants (1-7 wt %, relative to the organic phase). Significant differences in film properties were observed both as a function of amount and type of surfactant. Thermally reduced films exhibited concentration-dependent increases in surface roughness, electrical conductivity, and mechanical properties with increasing SDS content. When compared with SDBS, SDS films exhibited an order of magnitude higher electrical conductivity values at every concentration (highest value of ∼4.4 S m^-1 for 7 wt % SDS) and superior mechanical properties at higher surfactant concentrations. The present results illustrate how the simple inclusion of a benzene ring in the SDS structure (as in SDBS) can cause a significant change in the electrical and mechanical properties of the nanocomposite. Overall, the present results demonstrate how nanocomposite properties can be judiciously manipulated by altering the concentration and/or type of surfactant.