Yielding and structural transitions in sheared nanostructured soft matter

Abstract : well as the macroscopic mechanical properties of different soft matter systems such as polymers, colloids, emulsions and Langmuir monolayers. The coupling of shear flow with structure at different mesoscopic length scales gives rise to a rich non-linear behaviour such as shear thickening (an increase in viscosity with stress or shear rate), shear induced nonequilibrium phase transitions or flow instabilities accompanied by metastable shear induced structures. In my talk I will illustrate that combining rheological measurements with different imaging or scattering techniques (optical microscopy, light scattering and small angle X-ray scattering) to probe the structures at mesoscopic length scales (1 nm-1mm) is crucial for understanding these unusual flow properties observed in complex structured fluids comprising i) nanodispersions of carbon nanotubes [1] and Graphene Oxide [2] ii) liquid crystalline mesophases of surfactants [3] and iii) complex fluid-fluid interfaces formed by insoluble surfactants [4,5]. Gaining an insight into the mechanisms governing the complex interplay between microstructural transitions and flow is very relevant for controlling the structure of complex fluids in engineering applications, formulation of food products or cosmetics, shear force based drug delivery, 3D patterning of nanostructures under flow as well as the flow processing of nanocomposites.