Preparation and characterization of organoclays based on an amphoteric surfactant

The uptake of the amphoteric surfactant, cocamidopropyl betaine (CAB) by a sodium montmorillonite clay was studied with respect to concentration and pH. A series of organoclays was prepared in which the basal spacings were found to depend on both parameters. Adjusting the solution pH during preparation influenced the adoption of either 1.8 or 2.0 nm spacing, whereas the 3.9 nm spacing in the same sample was unaffected. The presence of the carboxyl group in the CAB molecule enabled dispersion of the clay at higher pH by which means pure organoclays of high spacing could be obtained, whereas, without dispersing the clay, mixed populations were obtained. The results indicate the optimum parameters for preparing organoclays of desired spacings for use in clay-reinforced nanocomposites.