EFFECTS OF SOLVENT STRUCTURE ON THE DISTRIBUTION OF SILICATE ANIONS IN MIXED AQUEOUS ORGANIC SOLUTIONS OF ALKALINE TETRAMETHYLAMMONIUM SILICATE

Effects of solvent structure on the equilibrium distribution of silicate oligomers in mixed organic/aqueous solutions of tetramethylammonium hydroxide (TMAOH) have been investigated by using Si-29 NMR spectroscopy. The results indicate that the presence of organic molecules leads to condensation of the silicates, particularly to double-ring structures. Equilibrium calculations indicate that the observed extent of silicate condensation exceeds what would be expected from mass action. The variety of organic solvents used allowed elucidation of structure effects due to the following: carbon chain length, carbon chain morphology, functional group, and placement of the functional group. The structural effects of organic solvents can be attributed to the ordering of water around the solvent molecules.