SOL-GEL POLYMERIZATION - ANALYSIS OF MOLECULAR MECHANISMS AND THE EFFECT OF HYDROGEN

The polymerization of silicic acid molecules (H4SiO4) was simulated using classical molecular dynamics with multibody potentials. The mechanisms involved in the condensation process were analyzed. Although a condensation mechanism was observed in the simulations which corresponds to the mechanism commonly assumed, additional mechanisms not previously presented were also observed. The advancement of polymerization was found to depend on the non-bridging oxygens' coordination with hydrogen, the number of bridging oxygens around five-coordinated silicons and atomic momentum. The results show consistency with the chemistry described for the acid catalyzed sol-gel process where hydrogen acts as the catalyst and chains form before rings.