Organofunctionalized RUB-18 from the intercalated precursor cetyltrimethylammonium cation

Crystalline layered sodium RUB-18 of the general formula Na2Si8O17·nH2O was organofunctionalized after prior cetyltrimethylammonium ion intercalation. The intermediate cetyltrimethylammonium-exchanged RUB-18 (CTA-RUB-18) was used with three different types of silane coupling reagents: 3-aminopropyltriethoxysilane (N), N-3-trimethoxysilylpropylethylenediamine (2 N) and N-3-trimethoxysilylpropyldiethylenetriamine (3 N). All silylated derivatives were successfully synthesized through a methodology based on the use of small amounts of the silylating agents, with the conventional reflux procedure. The organofunctionalized materials were characterized by X-ray diffraction, chemical analysis of carbon, hydrogen and nitrogen, infrared spectroscopy, thermogravimetry and scanning electron microscopy. The organosilyl pendant chains were covalently inserted onto the intercalated layered RUB-18 compound as shown by the structural evidence illustrated by 29Si and 13C NMR spectroscopy in the solid state. Correlations between the interlammelar distance (d) and the number of grafted organosilyl chains (n) on the silicate surface as a function of the number of atoms (na) in the pendant chains were obtained, represented by the equations: d = 0.65 + 0.32na and n = 3.71–0.29na, respectively. These synthesized inorganic–organic nanostructured hybrids may be applied for the construction of new nanomaterials, starting from hydrated layered silicates.