MESH SIZE OF TMOS GELS IN WATER

Silicon tetramethoxide monomers are dissolved in water, hydrolyzed, and condensed to form a mesh of siloxane polymers. The growth and aging of this gel are examined through light and X-ray scattering. From interferences at short distances, the fractal dimension, D, of the growing polymers is measured. From interferences at large distances, the mesh size, ξ, of the resulting network is measured, which scales with concentration: ξ is 400 Å when the volume fraction of polymer is φ = 0.04, and 10 000 Å when φ is 0.004. The scaling laws which are determined from the final state of the gel differ from those which describe its growth patterns. © 1990.