Modeling of alkyl quaternary ammonium cations intercalated into montmorillonite lattice

The objective of this work was to study the conformation of the quaternary ammonium cations viz., octadecyl trimethyl ammonium (ODTMA), dioctadecyl dimethyl ammonium (DMDOA) and trioctadecyl methyl ammonium (TOMA) intercalated within montmorillonite.The modified montmorillonite was characterized by X-ray diffraction in small angle (SAXS), thermal analysis (TGA) and infrared spectroscopy of attenuated total reflection (ATR).The modification of organophilic montmorillonites by the three surfactants ODTMA, DMDOA and TOMA increases the basal spacing from their respective intercalated distances of 1.9 nm, 2.6 nm and 3.4 nm respectively.The increase in the spacing due to the basic organic modification was confirmed by the results of thermal analysis (TGA) and infrared spectroscopy (ATR), and also supported by theoretical calculations of longitudinal and transversal chain sizes of these alkyl quaternary ammonium cations.

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► The modification of montmorillonites by three surfactants increases the basal spacing.
► The model proposed show a bilayer conformation for the surfactant ODTMA.
► The DODMA and TOMA surfactants adopt a paraffin type arrangement.
► Behavior of surfactants in interlayer space was confirmed by TGA and ATR analysis.