A method of synthesis of silicious inorganic ordered materials (MCM-41–SBA-1) employing polyacrylic acid–C nTAB–TEOS nanoassemblies

Abstract

In this work we describe the synthesis of a variety of MCM-41 type hexagonal and SBA-1 type cubic mesostructures and mesoporous silicious materials employing a novel synthesis concept based on polyacrylic acid (Pac)–C n TAB complexes as backbones of the developing structures. The ordered porosity of the solids was established by XRD and TEM techniques. The synthesis concept makes use of Pac–C n TAB nanoassemblies as a preformed scaffold, formed by the gradual increase of pH. On this starting matrix the inorganic precursor species SiO 2 precipitate via hydrolysis of TEOS under the influence of increasing pH. The molecular weight (MW) of Pac, as well as the length of carbon chain in C n TAB, determine the physical and structural characteristics of the obtained materials. Longer chain surfactants (C 16TAB) lead to the formation of hexagonal phase, while shorter chain surfactants (C 14TAB, C 12TAB) favor the SBA-1 phase. Lower MW of Pac (≈2000) leads to better-organized structures compared to higher MW (≈450,000), which leads to worm-like mesostructures. Cell parameters and pore size increase with increasing polyelectrolyte and/or surfactant chain, while at the same time SEM photography reveals that the particle size decreases. Conductivity experiments provide some insight into the proposed self-assembling pathway.