Maintaining Colloidal Stability of Polymer/Reduced Graphene Oxide Nanocomposite Aqueous Dispersions Produced via In Situ Reduction of Graphene Oxide for the Preparation of Electrically Conductive Coatings

Abstract

Chemical reduction of graphene oxide (GO) in an aqueous polymer/GO dispersion invariably causes restacking and precipitation of reduced GO (rGO) sheets leading to spontaneous phase separation. This has been a significant challenge limiting the commercial production of aqueous polymer/rGO paints and coatings. In this study, we developed in situ reduction strategies to chemically reduce GO while maintaining the colloidal stability of an aqueous polymer/rGO dispersion. An aqueous polymer/GO latex was prepared using miniemulsion polymerization, which was subsequently reduced in situ using four different chemical reducing agents (hydroiodic acid, sodium borohydride, ascorbic acid, and hydrazine hydrate) to obtain colloidally stable polymer/rGO dispersions. The reduction of GO was confirmed using X-ray photoelectron spectroscopy (XPS), Raman, and X-ray diffraction (XRD). The colloidal stability of the reduced dispersions was maintained for over 6 months under ambient storage conditions. Stable polymer/rGO dispersions were drop cast to form nanocomposite films at ambient temperature. Finally, the electrical conductivity measurement of polymer/rGO films revealed the highest conductivity for hydrazine hydrate-reduced films (∼6.6 S m–1), which was marginally higher than for hydroiodic acid-reduced films (∼3.4 S m–1). The electrical conductivity of sodium borohydride- and ascorbic acid-reduced films was two orders of magnitude lower than for hydrazine hydrate- and hydroiodic acid-reduced films. Overall, the present results pave a path for the commercial production of colloidally stable aqueous polymer/rGO composite paints and coatings.