Preparation and characterization of alkylamine-intercalated graphite oxides

Various n-alkylamine-intercalated graphite oxides were synthesized in the presence of a small amount of hexane and their compositions, chemical bonding and orientation of alkyl chains in them were characterized. The interlayer space of graphite oxide was saturated when about 11 mmol/g of n-hexadecylamine was included in it. Three types of alkylamines in GO were identified in the resulting intercalation compounds, hydrogen-bonded neutral amines, hydrogen-bonded protonated amines and ionically bound protonated amines, based on the infrared and XPS studies. The equilibrium between these species was established. Immersion of GO saturated by n-hexadecylamine in ethanol resulted in the de-intercalation of amines and the amount of residual amines was 3.0 mmol/g, which was rather similar to that of readily exchangeable protons in GO of 3.5 mmol/g. When alkyl chain length became shorter, the resulting intercalation compounds contained less alkylamine due to insufficient hydrophobic interaction between alkyl chains. The X-ray diffraction and polarized-infrared spectroscopic data indicated that alkyl chains of alkylamines took interdigitated monolayer and bilayer orientations for smaller and larger interlayer spacings, respectively.