Multi length scale analysis of the microstructure in sticky sphere dispersions during shear flow.

The effect of shear flow on the microstructure in a weakly aggregated suspension is investigated. Monodisperse small silica particles with a grafted layer of 1-octadecanol are dispersed in n-tetradecane, yielding a thermoreversible sticky sphere model suspension. A combination of small angle light scattering and ultra small and small-angle X-ray scattering techniques have been used, in situ and time resolved, to study the flow-induced anisotropy of the microstructure. In this manner, the length scales from the single particle size to that of the spatial organization of the aggregates can be covered. Harmonic expansion of the structure factor demonstrates that anisotropy develops in the microstructure on all relevant length scales. Possible real space interpretations of the scattering information are discussed in conjunction with implications for the nonlinear rheological behavior.