Superdiffusion of concentration in wormlike-micelle solutions

Our dynamic light scattering studies of viscoelastic wormlike-micelle solutions of surfactant cetyltrimethylammonium tosylate (CTAT) show superdiffusive relaxation of concentration fluctuations: relaxation rate &#8764;q<SUP>z</SUP> at wavenumber q, with z&lt;2, at concentrations just past overlap. Linear rheology experiments show that the micellar recombination kinetics in this system is diffusion-controlled (micelles break and recombine with their original partners). Addition of 10 mM to 100 mM of sodium chloride (NaCl), takes the system from the diffusion-controlled (DC) regime to mean-field recombination kinetics regime where micellar ends combine with ends belonging to other micelles. In the mean-field regime, the concentration fluctuations decay in a purely diffusive manner. We suggest a qualitative explanation for the observed superdiffusive behaviour in the DC regime