Physico-chemical control of sol-gel transition of titanium alkoxide-based materials studied by rheology

Viscoelastic characterization of titania-based sol-gel materials are investigated. Small amplitude oscillatory measurements are used to determine the gelation time t_g and the critical exponent of the frequency dependence of the loss and storage moduli. The scaling exponent is analyzed in order to estimate a fractal dimension at t_g. Hydrolysis molar ratio, titanium concentration and temperature parameters have an effect on the gelation time but not on the structure of the critical gel (gel at gelation time). However the acetylacetone concentration used as an inhibitor to control the reactivity of titanium seems to modify both the kinetic process and the gel structure.