MOLECULAR-DYNAMICS SIMULATIONS OF PHASE-SEPARATION IN THE PRESENCE OFSURFACTANTS

The dynamics of phase separation in two-dimensional binary mixtures di luted by surfactants is studied by means of molecular dynamics simulat ions. In contrast to pure binary systems, characterized by an algebrai c time dependence of the average domain size, we find that systems con taining surfactants exhibit nonalgebraic, slow dynamics. The average d omain size eventually saturates at a value inversely proportional to t he surfactant concentration. We also find that phase separation in sys tems with different surfactant concentrations follow a crossover scali ng form. Finally, although these systems do not fully phase separate, we observe a dynamical scaling which is independent of the surfactant concentration. The results of these simulations are in general in agre ement with previous Langevin simulations [Laradji, Guo, Grant, and Zuc kermann, J. Phys. A 44, L629 (1991)] and a theory of Ostwald ripening [Yao and Laradji, Phys. Rev. E 47, 2695 (1993)].