Mesostructural ultra thin silica film formation through admicellar technique

Abstract

Thin silica film formation from adsolubilization of inorganic silica precursors, letra-n-butoxysilane (TBOS) and tetraethyl orthosilicate (TBOS) in admicellar polymerization were studies. Cetyltrimethylammonium bromide (CTAB) at 700 uM and octyl phenol ethoxylate or Triton X-100 at 200 uM were used as surfactant templates for adsolubilizates TBOS and TBOS respectively. For the TBOS/CTAB system, the atomic force microscopy (AFM) topographic images showed fibers, hemispheres and flat layers existing along with increase of surface coverge on the mica surface as the TBOS feed concentration was increased. The results showed phase separation at low TBOS concentration, At high TBOS concentration, where there was no phase separation, the silica film was flat layer of multi-layer occurring from solublization of silicate anion of oligomers at the admicelle-aqueous solution interface. For the TBOS/ triton X-100 system, the surface morphology on the mica surfaceexhibited the thin homogeneous globular-shaped implying solubilization of TBOS at the admicelle-water interface. Addition of styrene monomer and 2.2-azobisosobutyronitrile (AIBN) initiator promoted adsolubilization of TEOS significantly in admicellar core of triton x-100. The surface morphology of the film depended on the amount of styrene and TEOS feed concentrations. As the styrene concentration increases, the periodic structures become more homogeneous. Higher concentration of styrene assisted the incorporation of TBOS in the polystyrene and inhibited the formation of silica particles on the surface, At 3 uM styrene and TEOS concentrations, styrene and TEOS synergistically fabricate the composite silica film with high coverage density.