**2. Experimental section**

242 Ion Exchange Technologies

preswelling step where by interlayer regions are exposed to quaternary ammonium [8,9,13]. However, preswelling procedures are problematic because they are complex, nonquantitative and require reagents. Recently, we reported a method of introducing metal alkoxides or organic precursors into H+-layered silicates without a preswelling step [14–18]. Layered materials have been often used to design and construct organic–inorganic nanomaterials because of the ease and variety of modifications possible by the introduction of organic and inorganic compounds into the interlayer space [19–27]. In recent years, the chemical modification into the interlayer surface of layered materials has become the focus of increased research. Ruiz-Hitzky and Rojo [28,29] grafted trimethylsilyl groups to the interlayer silanol groups of H+-magadiite starting with intercalation compounds from polar organic molecules. Shimojima et al.[30], Okutomo et al. [31], Ogawa et al. [32] and Yanagisawa et al. [33] reported on the trimethylsilylation, diphenylmethylsilylation and octyldimethylsilylation of magadiite, kenyaite and kanemite using the quaternary ammonium-exchanged form of silicates as intermediates. Thiesen et al. [34] also reported on

the silylation of H+-kenyaite using alkylamines together with a silylating agent.

heavy metal ions for photosensitive species.

We now report on the silylation of organic functional groups in the interlayer surface of a layered material. Functional organo-layered silicates with a functional group silylate in the interlayer surface can offer new opportunities for designing nanocomposites with the desired function because of their highly accessible interactions with various chemicals. In polymer–clay nanocomposite, physical properties depend on the interaction between exfoliated clay surfaces and the polymer. Interlayer surfaces bonded chemically by functional groups can interact with active groups in the polymer [35]. In particular, attached amine groups in the surface can chemically bond with epoxy [36], nylon [37], and urethane polymers [38], creating a bridge between the exfoliated layered surface and the polymer [35]. Their expanded gallery of functional groups can also store expensive reagents, such as drugs or enzymes. Layered materials with attached amine groups may be used to adsorb

Here, we found that the H+-titanosilicate (formed by proton exchange of Na+-titanosilicate) produced H+-titanosilicate/DDA (dodecylamine)/TEOS (tetraethylorthosilicate) intercalation compounds in DDA–TEOS solution. In these intercalation compounds, the long chain amine DDA appears to act as a gallery height expander and as a base catalyst during TEOS hydrolysis. Furthermore, it also appears to act as a liquid crystal template that forms surfactant-like molecular assemblies in galleries. The physical properties of the SPT derivatives produced were investigated by XRD (powder X-ray diffraction), BET (Brunauer, Emmett and Teller)-surface area, and SEM (scanning electron micrographs), and these investigations confirmed that SPT derivatives are mesoporous materials with large surface

Intercalation and silylation were easily achieved by entropy differences between the interlayer gallery and the outside, which were caused by vaporizing the relatively more volatile ethanol. The ethanol on the outside vaporizes more rapidly than that in the interlayer gallery. DDA can also have a role as gallery expander and silylation catalyst.

areas, highly ordered gallery structures, and high thermal resistances.

### **2.1. Synthesis of Na+-titanosilicate and H+-titanosilicate**

Na+-tanosilicate was prepared by the method described by Ferdov et al.[5]. SiO2 (14.8 g; particle size 200 μm, Merck) and 11.0 g NaOH (Junsei, Japan) were added to 200 ml of distilled water and completely dissolved by heating to boiling. Subsequently, 3.3 ml of TiCl4 (Yakuri Pure Chemicals Co., Japan) hydrolyzed in 100 ml distilled water was added to the above solution. The gel obtained was then transferred into 1000 ml Teflon-lined autoclaves. The crystallization was performed under static conditions at 180 oC for 50 h. The reaction product was filtered and washed with deionized water and dried at 40 oC. H+-titanosilicate was obtained by the ion exchange of Na+ in Na+-titanosilicate by H+ using 0.1 N HCl solution. A suspension of Na+ titanosilicate (10 g) in deionized water (200 ml) was titrated slowly with 0.1 N HCl solution to a final pH 2.0 and then maintained at this value for 24 h. H+-titanosilicate was recovered by filtering, washing with deionized water (until Cl- free), and drying in air at 40 oC.

### **2.2. Silica-pillared H+-titanosilicate (SPT)**

Silica-pillared H+-titanosilicate derivatives were prepared using methods similar to those reported by Kwon et al. [14,15], which introduce TEOS and DDA into the interlayer regions of H+-layered silicates without a separate preswelling step. Mixtures of H+-titanosilicate, DDA (Aldrich), and TEOS (Aldrich) at molar ratios in the range 1:10:14–20 were allowed to react for 1 h at room temperature. Here, DDA molecules intercalated into H+-titanosilicate interlayers by forming hydrogen bonds with interlayer surface Ti–OH groups. TEOS also intercalated with DDA by solvation. Mixtures at this stage were composed of DDA/TEOS co-intercalated H+-titanosilicate gels. Unreacted DDA and TEOS were removed by vacuum filtration, which resulted in the isolating of DDA/TEOS co-intercalated H+-titanosilicate gels. The hydrolysis of TEOS in interlayer spaces was conducted in pure water. The reaction was conducted by dispersing DDA/TEOS intercalated H+-titanosilicate gels in deionized water at room temperature, when the viscous gray gels became white solids. Bubbles and heat were also produced at 5 min into this reaction. After soaking for 30 min, the solid products obtained were filtered, washed three times with ethanol, and oven dried at 90 oC. Resultant powders were siloxane-pillared H+-titanosilicates. These powders were then heated for 5 h at 500 oC in air to remove template DDA, and organic by-products resulting from the hydrolysis of TEOS, to produce silica-pillared H+-titanosilicate (SPT) derivatives.

The SPT derivatives so obtained were also then heated for 5 h at 600 or 700 oC in air to examine their thermal resistances.
