Figure 6.

Turbidity scanning of the sol-gel reaction for 3F in water at pH 1.7 (a) and pH 3.0 (b). The graphs show light transmission vs. tube height, with 0 mm representing the bottom of the reaction tube. The lens of neat silane occupies the bottom ~2 mm of the 35 mm tube height, causing the dip in transmission seen at early times near the bottom of the tube. Hydrolysis solubilizes the silane, and the lens thickness narrows with time. Condensation in the bulk is observed by the drop in light transmission initially at the bottom and later through the entire length of the tube.