Structure and rheology during shear-induced crystallization of a latex suspension

Microstructure and rheology of a concentrated sterically stabilized colloidal suspension undergoing flow-induced ordering was studied by combined small-angle x-ray scattering and rheometry. This system is known to form bundlelike structures at high stress values in continuous shear flow. Under large amplitude oscillatory flow, hexagonal close-packed crystalline domains are formed within 1 sec of the inception of shear. In the intermediate range of frequencies and amplitudes, a nearly perfect hexagonally close-packed layer structure was observed after the cessation of flow. Lower frequencies or stress amplitudes resulted in polycrystals and, on the other hand, high frequencies or stress amplitudes led to partial melting of the layered structure. During the oscillatory flow, the intensity of the Bragg peaks showed pronounced oscillations.