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Issue 22, 2016
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The effect of charge separation on the phase behavior of dipolar colloidal rods

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Abstract

Colloids with anisotropic shape and charge distribution can assemble into a variety of structures that could find use as novel materials for optical, photonic, electronic and structural applications. Because experimental characterization of the many possible types of multi-shape and multipolar colloidal particles that could form useful structures is difficult, the search for novel colloidal materials can be enhanced by simulations of colloidal particle assembly. We have simulated a system of dipolar colloidal rods at fixed aspect ratio using discontinuous molecular dynamics (DMD) to investigate how the charge separation of an embedded dipole affects the types of assemblies that occur. Each dipolar rod is modeled as several overlapping spheres fixed in an elongated shape to represent excluded volume and two smaller, embedded spheres to represent the charges that make up the extended dipole. Large charge separations predominately form structures where the rods link head-to-tail while small charge separations predominately form structures where the rods stack side-by-side. Rods with small charge separations tend to form dense aggregates while rods with large charge separations tend to form coarse gel-like structures. Structural phase boundaries between fluid, string-fluid, and “gel” (networked) phases are mapped out and characterized as to whether they have global head-to-tail or global side-by-side order. A structural coarsening transition is observed for particles with large charge separations in which the head–tail networks thicken as temperature is lowered due to an increased tendency to form side-by-side structures. Triangularly connected networks form at small charge separations; these may be useful for encapsulating smaller particles.

Graphical abstract: The effect of charge separation on the phase behavior of dipolar colloidal rods

  • This article is part of the themed collection: Colloids
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Publication details

The article was received on 05 Feb 2016, accepted on 28 Apr 2016 and first published on 29 Apr 2016


Article type: Paper
DOI: 10.1039/C6SM00317F
Soft Matter, 2016,12, 4932-4943

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    The effect of charge separation on the phase behavior of dipolar colloidal rods

    D. M. Rutkowski, O. D. Velev, S. H. L. Klapp and C. K. Hall, Soft Matter, 2016, 12, 4932
    DOI: 10.1039/C6SM00317F

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