Brownian dynamics simulation of surfactant micellar microstructure and rheology

Three-dimensional Brownian dynamics simulation was conducted for dilute micellar surfactant solution under a steady shear flow and a steady uniaxial elongational flow. The rodlike micelle in the surfactant solution was assumed as a rigid rod made up of beads that were lined up. Lennard-Jones potential and soft-sphere potential were employed as the inter-bead potentials for end-end beads and interior-interior beads, respectively. The motion of the rodlike micelles was determined by solving the translational and rotational equations for each rod under hydrodynamic drag force, Brownian force and inter-rod potential force. Velocity Verlet algorithm was used in the simulation. The micellar microstructures and the rhelogical properties of the surfactant solution at different shear rates and elongation rates were obtained. The micellar network structure was formed at low shear or elongation rates and was destructed by high shear or elongation rates. The computed shear and elongational viscosities and the first normal stress coefficient showed shear thinning characteristics. The relationship between the rheology and the microstructure of the surfactant solution was revealed. The effect of surfactant solution concentration on the micellar structures and rheological properties was also investigated.