Confinement effects on the properties of Janus dimers.

Confinement has been suggested as a tool to tune the self-assembly properties of nanoparticles, surfactants, polymers and colloids. In this way, we explore the phase diagram of Janus nanoparticles confined between two parallel walls using molecular dynamics simulations. A nanoparticle was modeled as a dimer made by one monomer that interacts via a standard Lennard Jones potential and another monomer that is modeled using a two-length scale shoulder potential. This specific design of the nanoparticle exhibits distinct self-assembled structures and a water-like diffusion anomaly in the bulk. Our results indicate that besides the aggregates observed in bulk, new structures are observed under confinement. Also, the dynamic and thermodynamic behavior of the fluid phase is affected. The systems show a reentrant fluid phase and density anomaly. None of these two features were observed in bulk. Our results show that geometrical confinement leads to new structural, thermodynamical and dynamical behavior for this Janus nanoparticle.