Changes In The Morphology Of

(2006) Changes in the morphology of organoclays with HDTMA+ surfactant loading. Abstract The detailed understanding of the interlayer structure of organoclays is of importance in the design of organoclay based materials and their industrial applications. In this study, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) have been used to provide new insights into the interlayer structure and morphology of HDTMA + /montmorillonite organoclays. XRD patterns show that thermal treatment has an important effect on the stability of organoclays, reflected by significant changes in the basal spacing. TEM and SEM micrographs demonstrate that the organoclays with lower surfactant packing density are mainly composed of irregular layer stacking with a number of curved organoclay layers, while those with higher surfactant packing density are mainly composed of regularly intercalated and flat layers. Variations of the interlayer distances exist in all organoclays and are more pronounced in the organoclays with lower surfactant packing density. This study demonstrates that not only the arrangement model of surfactant but also the morphology of organoclay strongly depend on the surfactant packing density within the montmorillonite interlayer space. Introduction The study of organoclays is a vital subject in current research since various organoclays are widely used as nanocomposite precursors [1,2], adsorbents for organic pollutants [3], rheological control agents [4] and electric materials [5]. The combination of the hydrophobic nature of the surfactant and the layered structure of the silicate layers leads to unique physicochemical properties. In these applications, the behavior and properties of the organoclays strongly depend on the structure and the molecular environment of the organic molecules within the galleries. During the intercalation of the surfactants, the interlayer of the clay minerals is expanded as shown by the XRD patterns. A number of previous studies have demonstrated that the d-spacings of the organoclays depend on the length of the alkyl chains and the packing density of the surfactants within the galleries of clay minerals [6-11]. Accordingly, various models for the surfactant structural arrangements have been proposed chiefly based on XRD results. Recently, new approaches to the study of the surfactant structural arrangements including Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, Differential Scanning Calorimetry (DSC) and Magic-Angle-Spinning Nuclear-Magic-Resonance (MAS NMR) have been introduced to study the microstructure of organoclays and provided detailed conformational information [12-20]. However, these studies could not provide information about morphology and homogeneity of the organoclays.