LINEAR RHEOLOGY OF ENTANGLED WORMLIKE MICELLES

We report on the statics and dynamics of long and flexible wormlike mi celles made from cationic surfactants (cetylpyridinium ions) diluted i n brine (0.5 M NaCl) with strongly binding counterions (salicylate ion s). This survey was performed at ambient temperature by combining ligh t scattering and rheology measurements. Varying the weight percent, ph i, of surfactants from 0.1 % to 10 %, both dilute and semidilute regim es were studied. Above the crossover concentration phi approximately 0.3 %, the viscoelastic properties are described by an almost ideal Ma xwell relaxator. The overall rheological data are found to scale with the surfactant concentration with exponents close to those predicted f rom a recent stress relaxation model applied to living polymers. In ad dition, at high angular frequency, the complex elastic modulus results are interpreted in terms of crossover between the regimes of reversib le scission and of breathing of the polymer-like chains. Contrary to e arlier reports, the total average length of the micellar aggregates is found to increase with surfactant concentration as: L(phi)BAR approxi mately phi0.25-0.4.