Electrorheological properties of organically modified nanolayered laponite: influence of intercalation, adsorption and wettability

Abstract

Cetyltrimethylammonium bromide (CTAB) modified synthetic laponite is synthesized by an ion exchange method and characterized by simultaneous small-angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), atomic force microscopy (AFM), thermal analysis and rheometry. Through the formation of the organoclay, the properties of clay change from hydrophilic to hydrophobic. Morphology results show that the hydrophilic particles are aggregating easily, whereas the suitable CTAB modified laponite can get near monodispersed nanoparticles due to its hydrophobic properties. It is proposed that CTAB is intercalated and adsorbed onto the laponite partially depending on the substituted concentration of the surfactant cation exchange capacity (CEC) (0.5CEC to 6CEC). The electrorheological (ER) effect is investigated for suspensions of CTAB modified laponite dispersed in silicone oil. The two-dimensional SAXS images from ER bundles of CTAB modified laponite exhibit markedly anisotropic SAXS patterns, giving a measure for laponite particle alignment within the ER structure. An optimum electrorheological effect can be attained at a particular CEC substituted concentration. On the basis of the structure analysis and dielectric measurements, we attribute the enhancement of ER activity to the improvement in the dielectric properties that showed an increase in the dielectric constant and the dielectric loss at low frequency and their regular optimum change with CTAB modification.