Preservable superhydrophilicity of thermally cured graphene-nanoplatelets/epoxy nanocomposite coatings

This study aims to preserve the superhydrophility and the ultrafast water permeation property of the thermally cured graphene nanoplatelets (GNPs) coating after epoxy is added to enhance the adhesion of coating on its substrate. Addition of epoxy generally encourages the formation of carbon-carbon chain in the polymerization process during the thermal curing and the GNPs/epoxy nanocomposite becomes hydrophobic. On the other hand, the silver-filled epoxy can effectively suppress the crosslinking of carbon-carbon chain, enabling the thermo-oxidation process to take place where the oxygenated functional groups are attached on the edges of the GNPs. Hence, the use of silver-filled epoxy is capable to preserve the superhydrophilicity of GNPs. A series of comprehensive micro/nanoscopic and spectroscopic characterizations are performed to explain the significant difference in the wettability of the GNPs/epoxy nanocomposites. Molecular dynamics (MD) simulations are employed to elucidate the phenomena in the atomic resolution and nanosecond time scale. The MD results concur well with the characterization results, further verifying the proposed explanation of the interactions of carbon-filled epoxy and silver-filled epoxy with the graphene nanostructure during the thermal curing process. This study provides important insights into the analyses and characterization of the preservable superhydrophilicity of thermally cued GNPs/epoxy nanocomposites.