Kinetics of Diblock Copolymer Micellization by Dissipative Particle Dynamics

Micelle formation from a solution of randomly dispersed diblock copolymers in a selective solvent is found to be a three-stage process with a substantial contribution from kinetic processes involving small aggregates (dimers, trimers, etc.) and micelle fusion/fission resulting in a bimodal aggregation number distribution at intermediate times. Dissipative particle dynamics simulations were applied to study micellization kinetics and equilibrium properties of micelle solutions. The critical micelle concentration, micelle aggregation number distribution, and micelle structure were found to agree well with previous experimental and theoretical studies. The time-evolution of micelles from unimers is found to follow three stages: unimer consumption, equilibration of the number of micelles driven by the fusion/fission mechanism, and slow adjustment of the weight-average aggregation number by micelle fusion, unimer and small aggregate exchange. The effect of polymer concentration, hydrophobic interaction energy, and block length on the kinetics of micellization are also considered.