Relaxation phenomena in sol–gel transition

We performed a large set of quasi-elastic dynamic light scattering measurements of silica gels (tetramethoxysilicon) catalysed with NH 3 OH. Homodyne correlation functions were obtained during both slow and fast aggregation processes. In order to interpret our data we use a recently proposed model for relaxation in disordered systems, which selects two typical time scales in the process of approach to gelation. These times separate three different temporal regimes of exponential, power-law and stretched exponential decay. Our analysis allows a good description of the scaling regime associated with the decay and good values for the corresponding critical indices of the relevant quantities and the characteristic times close to gelation.