Mechanisms of the Exchange of Diblock Copolymers between Micelles at Dynamic Equilibrium

The exchange dynamics of chains between micelles of diblock copolymers in dilute solution in a selective solvent has been studied by a semianalytical approach. A close inspection of dynamic Monte Carlo simulation trajectories showed that there are mainly two types of exchange mechanisms, chain insertion/expulsion and micellar merger/splitting. The relative contributions of the two mechanisms to the overall exchange dynamics are examined as a function of the following variables:  the concentration of the diblock copolymers, the energy of interaction between the insoluble block and the surroundings, and the size of the insoluble block. A kinetic scheme, which incorporates the possible states of association and the mechanisms by which the exchange takes place, is constructed. The corresponding transition rates matrix, with the rate constants extracted from simulations, is used in a Master equation formalism to demonstrate that the two mechanisms involved in the exchange dynamics operate on time scales differ...