Self-assembly of polymer-grafted shaped nanoparticles provides a powerful avenue for the bottom-up fabrication of advanced plasmonic nanomaterials. Here, we investigate the underlying mechanism by which polymer-grafted nanocubes assemble into higher-order aggregates within a confined quasi-2D geometry. In particular, we compute the interaction free-energy landscape of such nanoparticles as a function of their separation distance and orientation using Monte Carlo simulations. The computed energy landscape reveals that the nanocubes exhibit two main stable states--the face-to-face and edge-to-edge configurations. The relative stabilities of the two states depend on the strength of vdW interactions between the nanocubes, the strength of interactions between the grafted polymer chains and nanocubes, and the length, grafting density, and excluded volume of the polymer chains. A scaling theory is developed to map out the orientation phase diagram of nanocubes within this extensive parameter space. The minimum free-energy path through the energy landscape reveals the key motions exhibited by the nanocubes as they approach each other and lock into their globally stable configuration. Analysis reveals that while the edge-to-edge forming cubes exhibit minimal motions during assembly, the face-to-face forming cubes undergo a transition from a cube-cube interaction-dominated sliding motion to a polymer-dominated rolling motion before they lock into their eventual bound configuration.

Assembly mechanism of polymer-grafted nanocubes

254th National Meeting (2017)

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