Kawamura Institute of Chemical Research ((KICR) Sakura-shi, JP) chemists reveal a nanofabrication process to produce monodisperse silica spheres containing a polymer with a linear polyethyleneimine chain, a compound having an acidic group, and silica in U.S. Patent 7,645,828. Inventors Ren-Hua Jin and Jian-Jun Yuan developed a process for producing the nano monodisperse spheres conveniently within a short time.
The monodisperse spheres have a functional molecule with luminance or the like with an organic acid group, and the bonded product is complexed with silica.
Silica spheres are used in an extremely wide range of applications, including from industrial uses such as in various additives or catalysts to products for everyday use. Furthermore, such silica spheres are being investigated from various aspects, for possible introduction of functional molecules or organic materials, or the like, in accordance with the characteristics that are required by various applications.
In order to produce silica (silicon oxide) in a desired shape from an aqueous sol-gel reaction, three critical conditions are considered to be indispensable. They are (1) a template for inducing the shape, (2) a scaffold for concentrating the silica source, and (3) a catalyst for polymerizing the silica source, according to the Kawamura Institute chemists.
The Kawamura Institute polymer (A) has a linear polyethyleneimine chain that is used as the organic material satisfying the above-described three factors. The linear polyethyleneimine chain is a rigid polymer chain having a secondary amine only in the main chain. The linear polyethyleneimine is soluble in hot water, but crystallizes at room temperature, thus existing as crystalline aggregates. Moreover, these crystals are dissolved in limited organic solvents only. This property is totally different to that of highly branched polyethyleneimine having primary, secondary and tertiary amines, which do not have a crystalline property and completely dissolve in water and common organic solvents.
The polymer (A) and silane are combined are obtained by performing a sol-gel reaction of an alkoxy silane in a mixed solvent (in the presence of water) under the catalytic effect of the ethylene imine structure in the polymer (A), using the stable aggregates obtained from the above as a template. The spheres obtained have an almost uniform particle diameter which can be determined by the structure of the polymer (A) and the compound (B) having an acidic group, and monodisperse silica spheres are achieved.
KICR’s research activities draw upon the institute’s expertise in nano- and micro-level polymer structural control and include such areas as biofunctional chemistry, nanocomposites, organic electronics, surface and colloid chemistry, and microfluidics.
FIG. 2 is a scanning electron micrograph of Kawamura Institute of Chemical Research monodisperse nano silica spheres