Growth and ripening of silica polymers in aqueous solutions

The molecular weights and number densities of polymers formed in neutral solutions of silicicacid, at the low concentrations that are typical of hydrothermal waters, were determined by gel filtration chromatography. The polymers exhibit Ostwald ripening that is characteristic of growth limited by a first order reaction of monomer at the surfaces of growing particles. Three divalent inorganic salts at 0.1 M are more effective at promoting polymer growth than is sodium chloride at the same concentration. The results support a recent theoretical model of the silica polymerization reaction but also identify ways in which the model might be improved.