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2008
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Nguyen TD, Zhang ZL, Glotzer SC
Molecular simulation study of self-assembly of tethered V-shaped nanoparticles
JOURNAL OF CHEMICAL PHYSICS 129, 244903
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View Abstract
We use Brownian dynamics to investigate the self-assembly of single end tethered, laterally tethered, and double end tethered V-shaped nanoparticles. The simulation results are compared with model bent-core molecules without tethers and polymer tethered nanorods to elucidate the combined effects of V-shaped geometry and the immiscibility between the V-shaped nanoparticles and the tethers on the self-assembled structures. We show that the V-shaped geometry significantly alters the phase diagram of tethered nanoparticles and further that the immiscibility between particles and tethers leads to structures not previously predicted for bent-core molecules. Examples of mesophases predicted include honeycomb, hexagonally packed cylinders, and perforated lamellar phases.
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Glotzer SC, Keys AS
Materials science - A tale of two tilings
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What do you get when you cross a crystal with a quasicrystal? The answer is a structure that links the ancient tiles of Archimedes, the iconic Fibonacci sequence of numbers and a book from the seventeenth century.
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Iacovella CR, Horsch MA, Glotzer SC
Local ordering of polymer-tethered nanospheres and nanorods
JOURNAL OF CHEMICAL PHYSICS 129, 044902
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We present results of Brownian dynamics simulations of tethered nanospheres and tethered nanorods. Immiscibility between tether and nanoparticle facilitates microphase separation into the bicontinuous, double gyroid structure (first reported by Iacovella et al. [Phys. Rev. E 75, 040801(R) (2007)] and Horsch et al. [J. Chem. Phys. 125, 184903 (2006)], respectively). We demonstrate the ability of these nanoparticles to adopt distinct, minimal energy local packings, in which nanospheres form icosahedral-like clusters and nanorods form splayed hexagonal bundles. These local structures reduce packing frustration within the nodes of the double gyroid. We argue that the ability to locally order into stable structures is key to the formation of the double gyroid phase in these systems.
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Vanipalli SA, Iacovella CR, Sung KE, Mukhija D, Millunchick JM, Burns MA, Glotzer SC and Solomon MJ
Fluidic Assembly and Packing of Microspheres in Confined Channels
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We study fluidic assembly and packing of spherical particles in rectilinear microchannels that are terminated by a flow constriction. First, we introduce a method for active assembly of particles in the confined microchannels by triggering a local constriction in the fluid channel using a partially closed membrane valve. This microfluidic valve allows active, on-demand particle assembly as opposed to previous passive assembly methods based on terminal channels and weirs. Second, we study the three-dimensional assembly and packing of particles against a weir in confined rectilinear microchannels. The packings result in achiral particle chains with alternating (zigzag) structure. This structure is characterized by a single, repeated bond angle whose components projected into the frame of the channel are quantified by confocal microscopy and image processing. Brownian dynamics simulation of the packing comprehensively delineates the range of bond angles possible in narrow, rectilinear microchannels as well as the complex dependence of these angles on the relative dimensions of the channel and particles. The simulations of the three-dimensional packings are accurately modeled by a compact theory based on trigonometric relationships. The experimentally measured bond angles show excellent agreement with the simulations, thereby validating the functional dependence of the achiral packing bond angles on channel dimensions. This functional relationship is immediately useful for the design of anisotropic particles by microfluidic synthesis.
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Carney RP, DeVries GA, Dubois C, Kim H, Kim JY, Singh C, Ghorai PK, Tracy JB, Stiles RL, Murray RW, Glotzer SC, Stellacci F
Size Limitations for the Formation of Ordered Striped Nanoparticles
Journal of American Chemical Society (In Press)
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