Mesoporous Silica Synthesized by Solvent Evaporation:  Spun Fibers and Spray-Dried Hollow Spheres

Abstract

Simple synthesis methods for mesoporous fibers and powders by rapid evaporation of hydrolyzed silicon alkoxide−surfactant solutions are described. Mesoporous fibers are prepared by dry spinning, and mesoporous powders by spray drying of alkoxide−surfactant solutions. Precursor solutions, containing fully hydrolyzed tetraethoxysilane, cetyltrimethylammonium chloride surfactant, and, in the case of the fibers, a fiber-forming polymer, in an acidic alcohol/water mixture, are drawn into continuous filaments or atomized into droplets in a heated air stream. During solvent drying, silica and surfactant self-assemble to form the hexagonally ordered mesophase structure, and all of the nonvolatile components (silica, polymer, and surfactant) are incorporated into the mesophase. The pore diameter and surface area of calcined fibers were 20 Å and 1100 m 2 /g, respectively. For the powders, pore sizes of 25 Å and surface areas as high as 1770 m 2 /g were measured. Spray-dried powders consisting of hollow spherical particles with mesoporous shells were also produced with this approach.