Determination of characteristic lengths and times for wormlike micelle solutions from rheology using a mesoscopic simulation method.

We apply our recently developed mesoscopic simulation method for entangled wormlike micelle (WLM) solutions to extract multiple micellar characteristic lengths and time constants: i.e., average micelle length, breakage rate, and entanglement and persistence lengths, from linear rheological measurements on commercial surfactant solutions, one containing sodium lauryl one ether sulfate (SLE1S), and the other containing both SLE1S and cocamidopropyl betaine, as well as a perfume mixture, in both cases with a sample salt (NaCl) added. Measurements include both mechanical rheometry and diffusing wave spectroscopy, the latter providing the high-frequency data needed to determine micelle persistence length accurately. By fitting the experimental data (G' and G") across the entire frequency range through our iteration procedure, the method is of practical use in predicting micellar parameters, which are difficult to obtain from other theoretical or experimental methods. The dependence of micellar parameters on added salt concentration, and the effect of micelle breakage mechanisms on viscoelasticity of WLM solutions, are also discussed. [ABSTRACT FROM AUTHOR]