SOL-GEL POLYCONDENSATION OF ALKOXYSILANES, STRUCTURE AND PROPERTIES OF SILOXANE MATERIALS

The sol-gel polycondensation of alkoxysilanes has been recently used f or the preparation of silicate materials called CERAMERs or ORMSILs wh ich found application in the production of various ceramic and glass p roducts for various fields. The reaction mechanism of the whole sol-ge l process has to be understood because properties of the products clos ely depend on the process of formation and reaction conditions. The kn owledge of kinetics and mechanism of the acid-and base-catalyzed hydro lysis and condensation is surveyed. The formation of basic building un its, their subsequent aggregation, formation and development of gel, g el structure, and chemical composition in the gel point, and changes i n the structure of siloxane network during drying are discussed. Some physical properties of gels and siloxane materials are compared as the y depend of the conditions of sol-gel process.