Shear Flow Behavior of Bidisperse Rodlike Colloids

A priori prediction of the flow properties ofpolydisperse rodlike macromolecules is a prerequisite for theunderstanding of many industrial and biological processes. Usingmixtures of two naturally monodisperse viruses, we create abenchmark bidisperse suspension of rodlike colloids to test theeffect of length bidispersity on the shear flow behavior. We findthat the zero-shear viscosity is a nonlinear function of the fractionof long rods because of the strong length dependence of therotational dynamics, which determine this quantity. Withincreasing concentration and fraction of long rods, the shearthinning gets more pronounced, following the predictions of ourrecently proposed theory which we extended for bidisperse mixtures. This theory allows for a quantitative prediction of the flow properties of bi- and polydisperse mixtures of ideal rods at least for moderate polydispersity