In Situ Surfactant Effects on Polymer/Reduced Graphene Oxide Nanocomposite Films: Implications for Coating and Biomedical Applications

Surfactants play a critical role in nanocomposite design and synthesis, ultimately influencing the intrinsic properties of the final nanocomposite material. From the perspective of development of nanocomposite coatings, targeting the ability to achieve uniform film formation on a range of substrates, there is an innate need to develop colloidally stable nanocomposite latexes. Given that surfactants are inevitably required to achieve colloidal stability of nanocomposite latexes, we herein explore surfactant influence on nanocomposite synthesis and the properties of the resulting films. More specifically, synthesis of electrically conductive polymer/reduced graphene oxide (rGO) nanocomposites is investigated via aqueous miniemulsion polymerization using two fundamentally different approaches toward polymer colloid stabilization, namely the use of (i) the conventional surfactant sodium dodecyl sulfate (SDS) and (ii) in situ surfactant formation using stearic and oleic acid/potassium hydroxide. Approach ii entails in situ formation of potassium stearate at the monomer droplet/water interface during emulsification. Simple drop-casting of the resulting nanocomposite latex followed by thermal annealing to reduce GO to rGO generates electrically conducting nanocomposite films. The different mechanisms of polymer particle stabilization greatly impact the electrical conductivity of the nanocomposite film─orders of magnitude higher conductivity is achieved by using the conventional surfactant approach. The present results provide important understanding and guidance for design and synthesis of functional hybrid films and coatings with a variety of potential applications particularly in coating and biomedical applications.