Directed self-assembly of Janus nanorods in binary polymer mixture: towards precise control of nanorod orientation relative to interface

The ability to control the organization of anisotropic nanoparticles, such as nanorods, with high precision would greatly facilitate the fabrication of functional materials. Using a hybrid computational model, we systematically investigate the directed self-assembly of Janus nanorods, with two chemically different surface compartments, in binary polymer mixtures. Our simulations demonstrate that the energetic contributions from the surface chemistry of the Janus nanorods, the rod-rod interaction, and the spatial confinement from the polymer phases can be tailored to tune the orientation angle of the nanorods with respect to phase interface, leading to the formation of "lying", tilt, and "standing" interfacial superstructures. A detailed insight into the mechanism regarding this precise control of nanorod orientation at the interface is obtained by evaluating the rod-phase interaction energy and the entropic energy of the tethered ligands on the rods. Furthermore, since the Janus rods are localized at the interface between two polymer phases, the structural evolution of the polymer nanocomposites is dramatically curtailed. This kinetic arrest is found to depend on the surface chemistry and the aspect ratio of Janus rods. The results demonstrated in this paper offer a novel approach to achieve morphological and kinetic control in nanoscopic composites towards unique photovoltaic and mechanical properties. A novel approach towards morphological and kinetic control in nanocomposites is theoretically demonstrated in the polymer nanocomposite containing Janus nanorods.