(450d) Rheology of Colloidal Suspensions and Gels

The rheology of concentrated colloidal suspensions with attractive and repulsive particle interactions is studied using FLD (fast lubrication dynamics) simulations. The microstructure is determined from dynamic simulations with results presented for varying strengths of attraction, range of attraction and volume fraction. Rheology studies are conducted to evaluate the relaxation modulus for viscoelastic response as well as the frequency dependence of the storage and loss moduli. Step strain /relaxation and oscillatory shear simulations yield consistent results for the moduli. Ensemble averaging and novel noise reduction algorithms are introduced to dela with the extreme. Rheological parameters are computed for a range of strengths of attraction, repulsion, range of attraction and volume fraction. The introduction of repulsive forces reduces the storage modulus by more than order of magnitude compared to attractive gels.