We identify two classes of rheology in solutions of wormlike micellar chains which break reversibly. In “mean-field” (MF) systems, new ends created by breaks recombine with other chains and stress relaxes exponentially [M. E. Cates, Macromolecules 20, 2289 (1987)]. By contrast, in “diffusion-controlled” (DC) cases, self-recombination dominates and the relaxation process is a Lévy walk, leading to algebraic short time decay. The long time decay remains exponential, but with a different time scale. Our estimates suggest that current experimental systems include both MF and DC types.

• Received 3 January 1995

DOI:https://doi.org/10.1103/PhysRevLett.74.4329