Atomistic Simulation Study of Striped Phase Separation in Mixed-Ligand Self-Assembled Monolayer Coated Nanoparticles

Atomistic molecular dynamics simulations are performed to study the stripelike patterns formed by phase separation of immiscible surfactants grafted on spherical surfaces. In previous work (Phys. ReV. Lett. 2007, 99, 226106), we showed that the formation of a striped phase for a mixture of two different length surfactants does not depend on the detailed chemistry of the molecules. Rather, the pattern is stabilized by increased conformational entropy related to the geometry of the molecules. In this paper, we extend the atomistic simulations of our earlier study to investigate the dependence of stripe thickness on charges on the head groups, the relative length difference of the tail, and the strength of the repulsion between the surfactants. Previously, we studied the dependence of the tilt angle for a homoligand surfactant on a nanoparticle surface (J. Phys. Chem. C 2007, 111, 15857). Here, we study the dependence of the tilt angle for mixed-ligand surfactants on a spherical nanoparticle surface. We observe that the tilt angle increases with surfactant length but does not play a significant role in stripe formation.