Sol-Gel process is a fine chemical synthesis process of inorganic materials such as ceramics, glasses, and hybrids. The process enables low-temperature, high purity and low cost fabrication of final solid materials. The process involves polymerization of monomers (small molecules) into colloidal solution (sol) by hydrolysis or condensation. Typical precursors (small molecules) are metal alkoxides. The sol acts like as “bigger precursor” for more integrated network of discrete particles or polymerization (gel) by drying or heating. More heating densified network and sintered into sol materials. The chemical process can fabricate the inorganic materials in the forms of thin film, bulk solid, aerogels, powders, fibers.

Metal alkoxides are ideal chemical precursors for sol-gel synthesis because they react readily with water. For fabrication of silica glass, the silicon alkoxides such as silicone tetraethoxides (Si(OC₂H₅)₄, tetraethyl orthosilicate, TEOS) are used. Alkoxides are hydrolyzed in the existence of water by acid- or base- catalyzed processes. The reaction is called hydrolysis, because a hydroxyl ion becomes attached to the silicon atom as follows:

The hydrolyzed molecules can link together in a water condensation (hydroxyl-hydroxyl reaction) and an alcohol condensation (hydroxyl-alkoxy reaction) to form siloxane linkage (Si-O-Si) as follows:

These types of reactions continue to build larger and larger siloxane molecules by the process of polymerization. Theses reactions are very dependent on water amount, kind of catalyst, pH, reaction condition, etc.

Thus, the sol-gel reaction of silicon alkoxides can be used as a chemical siloxane formation in the fabrication of inorganic-organic hybrid materials.