Molecular dynamics simulation and experimental study of micro‐structure and gel properties of single chain alkyl ammonium intercalated Na‐montmorillonite

Abstract

The synergistic effect of layer charge density of Na-montmorillonite (Na-MT), the carbon chain length and the dosage of alkyl ammonium on the microstructure and gel properties of single chain alkyl ammonium intercalated Na-MT was systematically studied by using X-ray diffraction (XRD), molecular dynamics simulation and small-scale experiment. The results of Z-axis density distribution and radial distribution function (RDF) shows that with the increase of the dosage of alkyl ammonium, the distribution pattern is gradually changed from layered to inclined winding and stacking distribution. The results of the self-diffusion coefficient show that the higher the layer charge density of Na-MT, the shorter the length of alkyl ammonium carbon chain, the lower the diffusivity of each component in the inter-layer. With the increase of the dosage of alkyl ammonium, the diffusivity of alkyl ammonium in the inter-layer increases firstly and then decreases. The results of gel properties show that with the increase of the dosage of alkyl ammonium, the colloidal ratio of the alkyl ammonium/Na-MT in xylene gradually increases, while the apparent viscosity in xylene-ethanol increases firstly and then decreases. Furthermore, the longer the carbon chain of alkyl ammonium, the lower the layer charge density of MT, the better the gel properties of the prepared alkyl ammonium/Na-MT.