مطالعه اثر كاتاليزور، زمان رشد و ماده فعال در سطح روي مشخصات پليمر معدني سيليكا

Study of Catalyst, Aging Time and Surfactant Effects on Silica Inorganic Polymer Characteristics

In the present study the sol-gel method is used for synthesis of amorphous nanostructure silica polymer using tetraethoxysilane (TEOS) as silicon source. This polymer can be used in manufacturing of nanoporous asym­metric membranes. The effect of catalyst on silica particle size has been studied under acidic and basic con­ditions. Acid-catalyzed reaction leads to the formation of fine particles while the base-catalyzed reaction pro­duces larger particles. The presence of cationic template surfactant namely cetyl pyridinium bromide (CPB) directs the structural formation of the polymer by preventing the highly branched polymeric clusters. This will increase the effective area of the produced silica membrane. Nitrogen physisorption tests by Brunaver- Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods revealed that the surface area of the mem­brane increases significantly around 5-folds when acid-catalyzed reaction is used. 29Si-NMR test is also used to study the aging time effect on the level of silica polymer branching. The results show that in acidic condi­tion, aging time up to three weeks can still affect branching. The calcinations process in which the organic materials and CPB (surfactant) are burned and released from the silica particles, is studied on template free silica materials as well as templated silica materials using TGA and DTA techniques.