Evidence for diffusion-controlled recombination kinetics in model wormlike micelles

We study the recombination kinetics and stress relaxation in a generic reversible polymer model, which is believed to resemble a wormlike micellar system. We find evidence that, at high concentrations, the recombination kinetics in this model cannot be described by a mean-field approach, but is diffusion-controlled and dominated by self-recombination events. We observe that the long-time stress relaxation of unentangled chains is proportional to v1/texp[-t/¿relax], with a relaxation time given by ¿relax = (th2/3¿ <L >1/3 where th is the average diffusion time to a different chain end, and ¿<L > is the characteristic relaxation time of a system of "dead" polymers of length equal to the average micellar length. A recombination activation barrier is needed to drive the system towards mean-field behaviour. This, in its turn, is often required in order to realistically model the rheology and dynamics of wormlike micelles.