Janus Nanorods in Shearing-to-Relaxing Polymer Blends

Although polymer nanocomposites containing Janus nanoparticles have demonstrated their powerful potential in the construction of ordered hierarchical structures with unique properties, less has been known about the shear behavior of these novel nanocomposites. Herein, Using systematic computer simulations, we investigate the structures and kinetics of binary polymer mixtures filled with Janus nanorods undergoing a shear field and the relaxing behavior of the same systems after ceasing shear. The results show that exerting shear facilitates the uniform alignment of these one-dimensional (1D) nanoparticles at the phase interface, along a dominant angle depending mainly on the ratio between two surface chemical compartments of the rods. The surface geometry of Janus nanorods also plays an important role in the structural morphology and kinetics of these polymer nanocomposites during the shear process. In the relaxing process after ceasing shear, it is interesting to find that the kinetics of these orientaionally hierarchical structures can be effectively arrested by tailoring the surface geometry of Janus nanorods. The rod rod interaction and the spatial confinement from polymer phases are also found to significantly influence the kinetics and the macroscopic alignment of nanorods in the relaxing process. Through theoretically analyzing various energetic contributions, we present the detailed mechanism for these self-trapped anisotropic sheared morphologies in the relaxing stage. These findings yield an effective and tunable route to achieve ordered and anisotropic arrays of 1D nanoparticles on a macroscopic scale, toward fabrication of polymer nanocomposites with robust photovoltaic and mechanical properties.