Two Methods for Intercalation of Surfactants into Graphite Oxide.
The intercalation properties of graphite oxide are important; however, the specific processes and mechanisms associated with intercalation have rarely been elucidated. In this paper, two types of surfactants, polyvinylpyrrolidone and tetradecyltrimethylammonium bromide, were used to thoroughly explore the intercalation properties of graphite oxide. The polyvinylpyrrolidone and tetradecyltrimethylammonium bromide-intercalated graphite oxide composites were synthesized under different conditions and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, and transmission electron microscopy. It was found that polyvinylpyrrolidone could be directly intercalated into the graphite oxide layers and tetradecyltrimethylammonium bromide could not effectively react with the waterdispersed graphite oxide. With a low quantity of polyvinylpyrrolidone, only a part of the graphite oxide was intercalated, and the interlayer spacing of the polyvinylpyrrolidone-intercalated composites increased as the polyvinylpyrrolidone: graphite oxide mass ratio increased. When the graphite oxide was dispersed in a 0.05 N NaOH solution, the tetradecyltrimethylammonium bromide rapidly reacted with the graphite oxide, while the mixture of polyvinylpyrrolidone and graphite oxide could not be effectively separated. The intercalated spacing of the tetradecyltrimethylammonium bromideintercalated graphite oxide increased with the tetradecyltrimethylammonium bromide: graphite oxide mass ratio, but its crystalline structure was not as ordered as the polyvinylpyrrolidone-intercalated graphite oxide prepared in the water solution. The infrared spectra of the two surfactant-intercalated graphite oxide samples revealed that the polyvinylpyrrolidone is bonded to the graphite oxide via hydrogen bonding, while the tetradecyltrimethylammonium bromide is bonded via ionic bonding. The mechanism analysis indicated that the polyvinylpyrrolidone could directly enter the graphite oxide layers in the water solution because of the driving force of hydrogen bonding. However, processes such as graphite oxide exfoliation, reactions between the graphite oxide and tetradecyltrimethylammonium bromide, and reaggregation of the graphite oxide sheets are necessary for the formation of tetradecyltrimethylammonium bromide-intercalated graphite oxide.