Rheology and flow dynamics of wormlike micellar gels

Long-chained zwitterionic surfactants form wormlike micellar (WLM) gels in solution at room temperature and revert back to a Maxwell viscoelasticity at higher temperatures. We study the rheology and flow dynamics of such WLM gels using a combination of rheometry and flow experiments. First, we rheologically characterize the material and reveal details of its microstructure along with signatures of shear-induced fracture and banding. Then we pump these WLM gels in a capillary pipe and measure the development of velocity profiles in time. Our experiments capture flow features like strong slip, plug and shear layers along with flow-induced heterogeneity. In the third part of the thesis we study droplet detachment and filament thinning of our WLM gels. We show the existence of elastocapillary thinning regimes, power-law failure and discuss dependencies of said dynamics on surfactant concentration. Our experiments reveal hitherto unknown complex dynamics even in simple flows of WLM gels and is likely to inform research on flows where rheology and transient fluid dynamics of similar soft matter systems play a crucial role.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat