Amine catalyzed condensation of tetraethylorthosilicate

The catalysis of the condensation of hydrolyzed metal alkoxides by amines has been mentioned in the literature, but there has been no systematic study of their influence on the rate of the condensation reaction of the alkoxide and the microstructure of the resultant gel. The hydrolysis of tetraethylorthosilicate (TEOS) was catalyzed by a mineral acid and the condensation was catalyzed by various organic amines. The gelation times were found to vary widely with the different amines used as the catalyst and the microstructure of the resultant xerogels also differed significantly depending on the amine added. Gelation occurred in the shortest amount of time when 1,4-diazabicyclo{2 2 2}octane (DABCO) was used, whereas, systems catalyzed with imidazole (Im) and pyridine (Pyr) and their derivatives exhibited longer gel times and were composed of less coarse microstructures.