Arrangement models of alkylammonium cations in the interlayer of HDTMA+ pillared montmorillonites
Arrangement models of alkylammonium cations in the interlayer of HDTMA^ pillared montmorillonites

The orientation of HDTMA+ in the interlayer of organic pillared montmorillonites prepared at different concentrations of HDTMA+ have been studied using X-ray powder diffraction (XRD) and theoretical calculation. A series of arrangement models of HDTMA+ in the interlayer of montmorillonite have been proposed as lateral-monolayer (LM), lateral-bilayer (LB), pseudotrilayer (PT), paraffin-type-monolayer (PM), paraffin-type-bilayer (PB). With the increase of the concentration of HDTMA+, the arrangement model of HDTMA+ in the interlayer of montmorillonites changes as lateral-monolayer→lateral-bilayer→para- ffin-type monolayer→pseudotrilayer→paraffin-type-bilayer and the packing density of HDTMA+ in theinterlayer increases gradually. In the intermediate stages, different models may coexist.