Surface modification of natural Na-montmorillonite in alkane solvents using a quaternary ammonium surfactant

The surface properties of a natural sodium montmorillonite (Na-MMT) was dramatically altered by a cationic surfactant dioctadecyldimethylammonium chloride (DODMAC) through an intercalation and ion exchange reaction in alkane solvents. Optical micrographs show that in situ organo-modification with surfactant DODMAC significantly improves the dispersibility of Na-MMT in alkane solvents. Changes in the structure and surface properties of the organophilic montmorillonite (OMMT) formed in octane, a volatile alkane, were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA/DTG) and Fourier transform infrared spectroscopy (FTIR). It is shown that organo-modification of Na-MMT surfaces based on ion exchange reaction in alkane solvents results in dispersion of the hydrophilic Na-MMT in the organic medium. And most importantly, viscosity curves of the clay suspensions suggest a potential method to control the rheological behavior of dispersions in alkane solvents instead of using organophilic montmorillonites. Furthermore, dispersion approaches and mechanism presented here will be useful for choosing compatibilizer and optimizing processing conditions especially in developing pristine-clay polymer nanocomposites.