Shear thickening in dilute solutions of wormlike micelles

A new mechanism is suggested for shear thickening in dilute solutions of wormlike micelles. According to this mechanism, there is an instability above a critical shear rate, c, by which micelles aggregate to form networks of bundles. We examine the first step of this instability by studying the aggregation of two micelles into a paired bundle. The model predicts that c is given by the inverse of the time necessary for the two micelles to unbind from each other. The order of magnitude and temperature dependence of the predicted c are in good agreement with experimental measurements. In addition, the model provides a natural explanation for the observation of coexistence between the shear-induced structure and a dilute phase at fixed shear stress.