DYNAMIC VISCOELASTICITY DURING SOL-GEL REACTIONS

The evolution of viscoelasticity during the gelation reactions of tetraethoxysilane solutions has been monitored from initial reactant mixing through the sol-gel transition with the multiple lumped resonator instrument. Gel points are determined by the observation of a frequency-independent loss tangent at a singular extent of reaction. The frequency dependence of G' and G" can be compared with recent theoretical models and simulations. Comparisons are made between the results for the chemical gel and the physical gel of gelatin. Again the occurrence of a frequency independent loss tangent corresponds to the macroscopic gel point.