Influence of the head group on dynamics in surfactant intercalated graphite oxide

Abstract

The influence of the headgroup on the dynamics of three different alkylammonium cations confined in graphite oxide (GO) was studied by temperature-dependent impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetry and elemental analysis served to characterize the composites. The alkylammonium cations were connected to the C–O⁻ group of GO via ionic interactions, and the backbone of the confined molecule was distributed as a flat monolayer with the long axis parallel to the GO layer. Ngai's correlated-state model was used, with asymmetry at low temperature in the loss peaks. The calculated true activation energy of 114 meV ± 6% meV is almost the same as the internal rotation barrier of the alkyl macromolecule. We conclude that the relaxation process is definitely attributed to the wobbling around the long molecular axes of the confined ions, an intrinsic motion, not the reorientation of C–H at the headgroup, and it is also due to geometric structural symmetry at the headgroup of the alkylammonium molecules with the interaction of their backbones and the skeletons of GO resulting in the difference in the apparent activation energy.