The shear-flow properties of telechelic polymer networks have been investigated by rheology and flow-visualization techniques. The steady-shear viscosity versus shear-rate curves exhibits two main branches separated by a discontinuity. One branch of the flow curve is Newtonian and shear thickening, whereas the second one is shear thinning. Above the discontinuity, shear induces a fluid fracture similar to those reported for brittle solids and at the origin of an inhomogeneous flow. Because of the finite relaxation time of the polymer network however, and contrary to ordinary gels, the fracture can be created and healed reversibly.

• Received 22 January 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.048303