Rheological and optical properties in systems containing TiO2 nanoparticles

In order to follow the sol–gel transition in systems containing TiO2 nanoparticles rheological and optical measurements were performed. Samples were prepared adding titanium(IV) butoxide (hydrolysis and condensation processes) to water/AOT/isooctane microemulsions. We prepared different systems at constant Wo=[H2O]/[AOT] while varying R=[H2O]/[Ti(BuO)4] to study the behaviour of viscoelastic parameters (G′, G′′ and η*) as a function of time at different frequencies as well as to analyse the Kerr constant (B) as a function of R. This work discusses the application of different theoretical approaches: scaling theory, ‘fractal growth model’ and ‘nearly linear growth model’. These experiments were complemented with light scattering measurements. Either static and dynamic optical determinations show an abrupt increase in the size of scattering particles. A significant increase in B values was observed for concentrations below gelification point when they were compared with those determined by light scattering.