Silica plates as precursor for nano-structured materials

Phyllosilicate clays are assemblies of nano-plates of silicate with the dimension of height to length being 1 : 100 nm or more. The preferential face-to-face stacking of these silicate plates via van der Waals forces leads to formation of lamellar, layered structures. The exfoliated (delaminated) structures of these lamellar clays offer advantages as precursor for formation of nano-structured materials. Various chemical treatments of the clays have resulted in the formation of delaminated, nano-plates of silicate (Si-O-M) or silica (Si-O-Si), which were incorporated in a polymer or dispersed in a liquid phase (Lin, et al., 2005). We present the results for formation of the delaminated, nano-plates of silica using an alternative, one-step treatment of these clays by an aqueous solution of acidic polymers. Experiments were carried out for the mixtures containing approximately 1% weight phyllosilicate in 5% aqueous solution of poly(acrylic acid) at different temperatures. X-ray diffraction and photoemission spectroscopy measurements for the solid products recovered after stirring the mixtures at 20 C showed that the fully extended chains of poly(acrylic acid) were intercalated within the interlayer spaces between the silicate plates of the clays. At 85 C, however, the clays were exfoliated. Photoemission spectroscopy and Fourier transform infrared spectroscopy indicated that the exfoliated structures were primarily consisted of silica nano-plates. These results further indicated that the silica plates are virtually free from impurities including polymeric residues.