(558be) Viscoelasticity and the Validity of Time-Concentration Superposition in Nanocolloidal Suspensions

Specific colloid-colloid and colloid-solvent interactions play a major role in governing the rheological behavior of nanocolloidal suspensions in which the solvent and the colloidal particles are of comparable sizes. With this motivation, we have created an explicit solvent model to determine the rheological features in the nanocolloidal suspensions. Unlike the mesoscopic simulation techniques, the hydrodynamics in these model systems are governed by the interparticle interactions. Molecular dynamics (MD) simulations are employed to determine the viscosity and the viscoelasticity moduli of these systems as a function of the colloidal volume fraction. The trends in the relative zero shear viscosity and the relative dynamic viscosity values as a function of the volume fraction are quantitatively consistent with the literature experimental, simulation, and theoretical studies. The Cox-Merz rule is observed to be applicable for our model systems. It is shown that the frequency range accessible to MD simulations can be extended by more than four decades by applying the time-concentration superposition (TCS) principle to the simulated modulus values. The master curves so obtained also follow the Kramers-Kronig relations.