Synthesis, characterization, and surface wettability properties of amine functionalized graphene oxide films with varying amine chain lengths.

Surface functionalization of graphene oxide (GO) an important graphene precursor using alkylamines of varying chain lengths followed by thermal treatment resulted in the formation of superhydrophobic surfaces. Alkylamines consisting of hydrophobic long chain alkyl groups and hydrophilic amine groups were chemically reacted to the GO surface via two types of reactions viz. (i) amidation reaction between amine groups and carboxylic acid sites of GO and (ii) nucleophilic substitution reactions between amine and epoxy groups on GO surface. Successful grafting of alkylamines was confirmed using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance ((1)H NMR), and thermogravimetric analysis (TGA). Alkylamine-modified GO surfaces showed enhanced roughness, and this effect was more pronounced with increasing amine chain length. Water contact angle measurements revealed that the hydrophobic nature of graphene depended on the chain length of the grafted alkylamines, and this fact may be corroborated to the decrease in the surface energy values. Our results indicate that superhydrophobic graphene films can be produced by thermal treatment of hexadecylamine- and octadecylamine-grafted GO films. These results will provide valuable guidance for the design and manufacture of graphene-based biomaterials, medical instruments, structural composites, electronics, and renewable energy devices.