DYNAMICS OF SELF-ASSEMBLED SURFACTANT SYSTEMS

The dynamics of self-assembling systems were investigated for the mode l amphiphile A(2)B(2) using stochastic dynamic simulations. Temperatur e jump computer ''experiments'' were performed and the evolution of th e system to its new equilibrium state monitored, The results were inte rpreted based on the Aniansson-Wall theory of micellar kinetics, The t ransient behavior predicted using the Aniansson-Wall theory agrees wel l with the simulated data, particularly at short times. At long times, deviations are observed which may be ascribed to errors in estimating the dissociation rate and number density of aggregates in the all imp ortant micelle-depleted zone. The micellar dissociation constant was c alculated from independent tagging simulations. The amphiphile exit ra te constant was calculated at different temperatures from which an act ivation energy associated with the removal of a surfactant chain from a micelle was found to be of order 10-15 kT and to be independent of t he friction coefficient. Finally the Helmholtz free energy profile ass ociated with the extraction of a surfactant chain from a micelle was d etermined. A free energy barrier height of order 5 kT was obtained. Kr amers' rate theory was employed to determine the corresponding exit ra te constant which was found to be in excellent agreement with the resu lts obtained from tagging runs, the barrier height associated with the insertion of a surfactant chain was order 1 kT, suggesting that the a ssociation process is diffusion controlled. (C) 1998 American Institut e of Physics.