Self-assembly in two-dimensional mixtures of Janus disks and isotropic particles.

Using Monte Carlo simulations, we investigate the self-organization of Janus disks and small isotropic particles in two-dimensional systems. In our model, a Janus particle contains an attractive part, A, and an repulsive part, R. The isotropic particles are strongly attracted by the R-part and repelled by the A-part. The number of Janus particles is fixed, while the number of isotropic particles varies. As the concentration of isotropic particles increases, the system structure changes. We show that the size of Janus disks strongly affects the system morphology. In the case of big Janus particles, we have found a lamellar-like phase and a gel-like structure. Different structures are formed in mixtures with smaller Janus particles. At sufficiently high densities of isotropic particles, Janus particles always aggregate into small clusters that are evenly dispersed in the "sea" of isotropic particles. The energies of interactions between both species are analyzed. The mechanism of co-assembly is discussed.