The preparation and characterization of cetyltrimethylammonium intercalated muscovite

Abstract

A new method to prepare alkylammonium–muscovite nanocomposites is reported. The intercalation of alkylammonium into muscovite could be obtained by two steps: the inorganic–inorganic ion exchange and the inorganic–organic ion exchange under hydrothermal condition. The intercalation at different alkylammonium concentration has been studied by elemental analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The cetyltrimethylammonium cations enter the interlayer of muscovite and anchored to the aluminosilicate layer through strong electrostatic interaction. A threshold of cetyltrimethylammonium concentration exists with the maximum ion-exchange percentage of 50%. The arrangement, conformation and orientation of alkylammonium tail and the distribution of headgroups show strong dependence on alkylammonium concentration. At lower alkylammonium concentration, the alkylammonium cations are lying on the aluminosilicate layer to form a monolayer structure, taking disordered conformation and headgroup distribution. With the increase of concentration, the alkyl tails begin to radiate away and stand up from the aluminosilicate surface; meanwhile, the distribution of headgroups become well, and the arrangement and conformation of chains become more ordered. For samples with concentration beyond the threshold, the alkylammonium headgroups are distributed on aluminosilicate layer uniformly, and the alkylammonium chains are in a paraffin-like arrangement with a titled, fully stretched all-trans conformation.