Ring-driven shear thickening in wormlike micelles?

The shear-thickening behaviour of wormlike micelles, at concentrations just below “overlap”, remains unexplained. In some cases, it has recently been confirmed that very slow relaxations must be present even in the quiescent state —for example, the shear-thickening properties can depend on earlier thermal cycling. We present a speculative scenario based on the presence, just below the (apparent) overlap threshold, of large rings whose linking and delinking kinetics control the shear-thickening process. Equilibration between rings and open chains in turn controls the slow relaxations.