Formation of Layered Silica-Alcohol Nanostructured Materials from Alkoxytrichlorosilanes

Novel layered silica-organic nanostructured materials were prepared by hydrolysis and condensation of alkoxytrichlorosilanes (n-C_nH _2n+1OSiCl₃, n = 12, 14, 16, 18, and 20) as single precursors. The formation relies on the self-assembly of alkoxysilanetriols (n-C_nH_2n+1OSi-(OH)₃) generated by the preferential hydrolysis of Si-Cl groups in the precursors. The products exhibited the XRD patterns indicative of layered structures whose d spacings varied in the range of 3.95 to 6.13 nm depending on the alkyl chain lengths. The SEM images of the products showed well-defined platelike morphologies on micrometer length scales, reflecting the layered structures of the products. Further structural characterization by solid-state ²⁹Si and ¹³C NMR and FTIR revealed that the layered structures consisted of bimolecular layers of long-chain alcohols and thin silica layers. Condensation of alkoxysilanetriols proceeded in the solid state to form silica networks, being accompanied by the cleavage of the alkoxy groups. The present results provide a new approach for the construction of silica-based nanostructured materials with well-regulated organic arrays and silica networks.