(629f) Fast and Slow Dynamical Processes in Simulations of Block Copolymer Micelles

Experimental studies of dynamics in micellar solutions of small molecule surfactants show evidence of “fast” and “slow” processes with widely disparate time . The “fast” process is associated with insertion and expulsion of individual surfactant molecules, while the “slow” process is associated with creation and destruction of entire micelles. We discuss a simulation study of rates and mechanisms of both fast and slow processes in a simple coarse-grained model of “hairy” diblock copolymer micelles of highly asymmetric copolymers. Quantitative study of rates of insertion and expulsion show that insertion rates in this model are essentially diffusion controlled, and that the micelle corona does surprisingly little to hinder exchange of individual molecules. Study of the rates of the slow process focus on a comparison of predicted rates for micelle creation and destruction by postulated competing pairs of processes of (1) step-wise association and dissociation and (2) fission and fusion of entire micelles, in order to clarify which of these processes controls relaxation of the micelle size distribution.