Time-dependent properties and microstructure in colloidal dispersions

The balance of hydrodynamic and interparticle forces determines the microstructure and the macroscopic behavior under flow in nanocomposites. Flow can induce structural changes which manifest in a variable viscosity. If the changes are reversible and time dependent, the effect is called thixotropy. The time scales associated with this structuration are typically slower than the classical viscoelastic time scales of the components but faster than the slow phenomena due to ageing or degradation. A proper understanding of the thixotropic flow characteristics allows to solve complex industrial problems. By using different types of model particles in polymeric media of different rheology, we can probe the effect of varying particle-particle and particle-matrix interactions on the thixotropic behavior. In addition, gradually changing the molecular weight of the matrix allows us to study the competition between the time scale associated with the particulate network and the time scale associated with the inherent viscoelasticity of the matrix polymer. As such, we are able to develop a rationally based general understanding of the structure development in nanocomposites.status: publishe