Résumé
During pendant drop experiments, a model physical gel made from oil in water microemulsion droplets reversibly linked together by triblock copolymers, exhibit a very peculiar filament rupture corresponding to highly brittle failure of a viscoelastic fluid. The fracture propagation has been tracked by high speed videomicroscopy. Analysis of the time evolution of the fracture profile shows that the fracture is purely elastic and reversible without any significant bulk and interfacial viscous dissipation. However, since the elastic moduli of such complex fluids are low, hyper elastic corrections have to be taken into account for a quantitative analysis of the fracture profile. This brittle behavior is well explained by a hyperelastic generalization of the viscoelastic trumpet model of de Gennes. The velocity of the fracture's propagation is measured and compared to the predictions of a simple microscopic model.