DYNAMICS OF WORMLIKE MICELLES - THE BOND-INTERCHANGE REACTION SCHEME

We study theoretically the dynamics of systems of elongated wormlike micelles which undergo ''bond-interchange'' reactions. Bond-interchange reactions may occur when two micelles come into contact at some point along their arc lengths. A transient structure resembling a four-armed star polymer is formed briefly, decaying to give two new micelles with each section of the first micelle fusing to one or other section of the second. First we consider the relaxation of the molecular weight distribution (MWD) of a system of wormlike micelles after an arbitrary (material conserving) perturbation to the MWD. We show that bond-interchange reactions do not provide a pathway for the relaxation of the MWD to equilibrium. Second we consider the dynamics of entangled systems of wormlike micelles. We calculate the scaling of the terminal time, viscosity, and monomer diffusion constant with the volume fraction of surfactant in the regime where micellar reactions are rapid on the time scale of reptation. These results may help in identifying systems in which bond-interchange reactions occur. Finally we discuss the validity of the ''tube'' model in these systems. We consider when a description based on the tube model is appropriate, given that bond-interchange reactions allow chains to pass through one another.