Abstract

Catanionic surfactant systems are used as drug-delivery vehicles and as nanocompartments in the formation of biomaterials and nanosized particles. Clay minerals are compatible with organic tissues and also have biomedical applications. The aim of the present study was to combine the properties of catanionic surfactants and clay minerals to obtain new materials with potential uses in medicine, waste-water treatment, and antibacterial applications. The surfactants chosen to make the catanionic surfactant were cetylpyridinium (CP) and lauroyl sarcosinate (SR), which interact strongly in aqueous media and cause specific aggregations such as ion-pair amphiphiles and needle- and leaf-like structures. Aside from the aqueous solution, new ternary systems are formed with different structures and properties through the addition of montmorillonite (Mnt). The surface and interlayer structures of the different Mnt-CP-SR samples prepared by using CP and SR in amounts equal to various ratios of cationic exchange capacity of the clay mineral were studied. They were also compared with the structured surfactant aggregates formed in aqueous media. The Mnt-CP-SR samples were subjected to X-ray diffraction (XRD), thermogravimetric analyses, and zeta-potential measurements to elucidate the interlayer- and external-surface structures. The XRD analyses showed the formation of a compact structure in the interlayer region resulting from the interaction between randomly oriented pyridinium and negatively charged SR head groups. The triple interactions among the Mnt surface, CP, and SR were more complex than the double interactions between the Mnt and cationic surfactant, and the CP played a dominant role in the formation of external and interlayer surface structures regardless of the amount and order of the addition of SR. The new findings support new applications for organoclays in the fields of biomedicine, remediation of polluted water, and nanocomposite materials.

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