Highly transparent sol-gel derived ureasilicate monoliths exhibiting long-term optical stability

Optically clear and elastic organic-inorganic hybrid materials were synthesized by hydrolysis and condensation of ureasilicate precursors. Ammonia or citric acid was used as a catalyst for hydrolysis and condensation reactions. The influence of the catalyst nature and the precursor content on the optical, mechanical and thermal properties of samples was investigated. It was shown that it is possible to significantly change the elastic properties of the ureasilicates keeping their good optical transparency in the visible range. The preparation conditions assuring long-term optical and mechanical stability of the samples were determined.