Dissertation/Thesis Abstract

Phase behavior of charged hydrophobic colloids on flat and spherical surfaces
by Kelleher, Colm P., Ph.D., New York University, 2017, 194; 10195879
Abstract (Summary)

For a broad class of two-dimensional (2D) materials, the transition from isotropic fluid to crystalline solid is described by the theory of melting due to Kosterlitz, Thouless, Halperin, Nelson and Young (KTHNY). According to this theory, long-range order is achieved via elimination of the topological defects which proliferate in the fluid phase. However, many natural and man-made 2D systems posses spatial curvature and/or non-trivial topology, which require the presence of topological defects, even at T=0. In principle, the presence of these defects could profoundly affect the phase behavior of such a system. In this thesis, we develop and characterize an experimental system of charged colloidal particles that bind electrostatically to the interface between an oil and an aqueous phase. Depending on how we prepare the sample, this fluid interface may be flat, spherical, or have a more complicated geometry. Focusing on the cases where the interface is flat or spherical, we measure the interactions between the particles, and probe various aspects of their phase behavior. On flat interfaces, this phase behavior is well-described by KTHNY theory. In spherical geometries, however, we observe spatial structures and inhomogeneous dynamics that cannot be captured by the measures traditionally used to describe flat-space phase behavior. We show that, in the spherical system, ordering is achieved by a novel mechanism: sequestration of topological defects into freely-terminating grain boundaries (“scars”), and simultaneous spatial organization of the scars themselves on the vertices of an icosahedron. The emergence of icosahedral order coincides with the localization of mobility into isolated “lakes” of fluid or glassy particles, situated at the icosahedron vertices. These lakes are embedded in a rigid, connected “continent” of locally crystalline particles.

Indexing (document details)
Advisor: Chaikin, Paul M.
Commitee: Donev, Aleksandar, Grosberg, Alexander, Pine, David, Sleator, Tycho
School: New York University
Department: Physics
School Location: United States -- New York
Source: DAI-B 78/08(E), Dissertation Abstracts International
Subjects: Physics, Condensed matter physics, Materials science
Keywords: Colloidal particles, Melting, Phase behavior
Publication Number: 10195879
ISBN: 978-1-369-63006-0
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