Dynamic oscillatory experiments are used to monitor the gelation of the
borosilicate systems prepared through the sol-gel process from metal
alkoxides. The rheological experiments show that tan δ = G”/G’ is
independent of frequency at the gel point in agreement with the results of
others on organic gelling systems. The dynamic moduli at the gel point
followed power-law behavior with respect to frequency. The power-law
exponent is found to be ∼0.70. The apparent fractal dimension, dp, of the
network cluster at the gel point is determined. The dF values for
the samples ranged from 2.5 to 3.8 depending on the final structure of the
evolved products at the gel point. The large values (dF > 3)
exclude a simple geometric interpretation of the results. The effect of
processing parameters, such as composition of reactants and temperature, on
the resulting microstructures near the gel point is discussed.