Shear orientation of nanoparticle arrays templated in a thermoreversible block copolymer micellar crystal

The shear alignment of binary crystals of polymeric micelles and small particles is demonstrated using contrast-variation SANS experiments. The larger micelles form close-packed crystals that serve as a template to the smaller nanosized particles. The simultaneous alignment of the two phases, micelles and templated particles (silica or albumin proteins), is demonstrated from the scattering at two different contrast values. A new method to quantify the alignment of colloidal crystals using diffraction is also proposed. This method is used to probe the alignment of the crystals as a function of shear rate. It is found that the binary crystals align at significantly lower shear rates when compared to the neat micelle crystals. The diffraction profiles of the cocrystals are compared to models for the flow mechanism of colloidal crystals. Differences between the experimental profiles and the predictions suggest that there is a coexisting crystal phase that is not accounted for in the model.