(272b) Icosahedral Packing of Polymer-Tethered Nanospheres and Stabilization of the Gyroid Phase

The use of polymer tethered nanoparticles provides a unique method to control the self-assembly of nanoparticles into ordered mesophases that resemble the complex morphologies of block copolymers. We present results of molecular simulations that predict the phases formed by the self-assembly of attractive model nanospheres, where each nanosphere is functionalized with a single polymer ?tether?. Microphase separation of the immiscible tethers and nanospheres induces the formation of hexagonally packed cylinders, the double gyroid phase and perforated lamellar phases with distinct icosahedral order between nanoparticles. Confinement effects promote the formation of these icosahedral arrangements of nanoparticles and help to stabilize the gyroid phase by reducing packing frustration. We also find the presence of lamellar bilayers with crystalline order among nanoparticles. Additionally we present a new metric for determining the local arrangement of particles based on spherical harmonic ?fingerprints? of reference structures, where a residual minimization scheme is used to accurately determine the local structure.