Influence of clay charge densities and surfactant loading amount on the microstructure of CTMA–montmorillonite hybrids

Abstract

Influences of both charge characteristics of montmorillonite and loading amount of cetyltrimethylammonium cations (CTMA +) on the microstructure of CTMA–montmorillonite hybrids were examined to present some novel information about structural characteristics of the surfactant–clay hybrids. Various amounts of CTMA + were intercalated into montmorillonite hosts with different layer charges, and microstructures of the obtained CTMA–montmorillonite hybrids were characterized with X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR). Experimental results showed that basal spacing of the hybrids and packing density and ordering of the adsorbed surfactant increased with surfactant loading amount and clay layer charge density. Combining the characterization results with the surfactant intercalation mechanism the structural models of the hybrids were proposed. For the first time heterogeneous distribution of the intercalated surfactants was considered in these models, not only between adjacent interlayers but also within the same interlayer, which could be ascribed to the formation of surfactant “islands” in the surfactant intercalation process and the heterogeneous distribution of layer charges on the hosts. Results of this work also indicated that it is possible to regulate the structures of the surfactant–clay hybrids by simultaneous control of the surfactant loading amount and the clay charge characteristics.