Macroscopic response of wormlike micelles to elongational flow

Opposed nozzle flow is used to measure the elongational properties of wormlike micelles. Well-characterized semidilute micellar solutions of CPCl/Sal in concentrated brine are used, By varying temperature and concentration, the viscoelastic properties (tau(R), G(0)) of the equilibrium solutions can be controlled and the influence of viscoelasticity on elongational viscosity probed. Results indicate three regimes of steady elongational behavior: a constant viscosity at low elongational rates, an increase to a maximum viscosity, and then a subsequent drop in viscosity. Scaling of the macroscopic elongational properties with linear viscoelastic parameters and similarities between these solutions and entangled polymer solutions indicate that semidilute CPCl/Sal solutions do not exhibit significant changes in micellar structure and may provide model systems for studying the influence of complex flow fields on entangled polymer solutions.