Barrier Properties of Polymer Nanocomposites with Graphene Oxide and Its Derivatives: Mechanism and Applications in Anticorrosive Coatings

Metallic devices made from steel or aluminum are subjected to deterioration by environmental contaminants over time. As one of the corrosion control methods, organic coatings show many advantages due to their low cost, versatility, decoration aesthetics and effective protections. Corrosion protection theories and failure modes of organic coatings are still not fully understood due to complicated interactions in the coating-metal-environment system, however, it is widely agreed that the barrier nature of polymeric materials towards aggressive species, such as oxygen, water, electrolyte, plays a key role. Improved barrier property of polymer nanocomposites (PNCs) with two-dimensional (2D) carbon filler, graphene and graphene oxide (GO), has been extensively studied in the areas of membrane science and packaging materials, however, a systematic study on their applications as protective coatings is still rare. In this work, we describe the fabrication and modification of PNCs containing GO and GO derivatives in an effort to formulate organic coatings with improved barrier properties and corrosion resistance. Impacts of GO and GO derivatives upon oxygen permeability and water resistance of their PNCs were studied and correlated to their corrosion protection properties. In the first study, functionalized GO containing reduced hydrophilic moieties were synthesized by the reaction between hydroxyl group (–OH) on GO and α-bromoisobutyrl bromide, with the intent of reducing water sensitivity while maintaining high oxygen barrier property of the resulting latex nanocomposites fabricated via aqueous blending with styrene-acrylic copolymer latex. The second study focused on the development of a facile efficient protocol for synthesizing GO derivatives by using a designed low-density aerogel precursor, which exhibits improved reactivity in many organic solvents with low polarity. Hydrophobically modified GO was prepared using small-molecule (hexanoyl chloride) and oligomeric (amino terminated) polyisobutylene (PIB) modifier(s), and thoroughly investigated for their surface properties. In the third study, a bilayer coating of waterborne epoxy-amine resin based composites was designed to provide improved water and oxygen barrier properties by incorporating GO lamellae in the bottom layer and hydrophobic polymer additive in the top layer. The resultant bilayer coating exhibits improved corrosion protection property in simulated corrosive environments due to reduced surface wettability and decreased oxygen permeability