On the preparation, characterization, and application of Janus spheres
Item
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Title
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On the preparation, characterization, and application of Janus spheres
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Identifier
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d_2009_2013:d585a67a90e1:09980
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identifier
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10075
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Creator
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Cui, Jingqin,
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Contributor
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Ilona Kretzschmar
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Date
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2009
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemical engineering | Materials science | acrylate | electroactive polymer | electroless deposition | Janus particle | PDMS | surface-anisotropic
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Abstract
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Surface-anisotropic Janus particles are a new class of materials with interesting properties that have attracted great attention recently. There have been many reports on the manufacture of Janus particles. However, most of them employ the traditional high-cost vapor phase deposition to obtain an asymmetric surface modification of particles.;In this thesis, a novel templating process is developed for the manufacturing of Janus spheres via the economic and mild electroless deposition (ELD) method. Templated micron- and submicron-sized polystyrene (PS) spheres are modified with a silver cap composed of 50-200 nm nanoparticles (NPs) through the ELD process. The deposits are found to be stable over time and under physical treatment. Further, the study determines that the substrate sphere curvature influences the ELD modification due to the functional group coverage and distribution as well as the size ratio of the substrate sphere to the NPs deposit. Gold, palladium and titanium oxide particles are successfully deposited onto PS spheres using the same templating process and nanoparticle synthesis methods from literatures in the electroless/wet chemical deposition.;Modifications obtained with the ELD conditions studied exhibit a rough surface compared to the vapor-phase modified surfaces. The surface roughness is controlled by varying the ELD reaction conditions to adjust the amount of deposit and the size distribution of the NPs deposited. The assembly of Janus spheres with smooth caps produces planar 2-D structures while spheres with rougher caps tend to form 3-D cluster structures, implying that the surface morphology has an effect on the sphere-sphere interactions. The assembly of new dual-cap/mono-belt Janus particles prepared by combining the vapor phase and ELD processes confirms that the surface roughness influences the orientation of the Janus spheres during assembly.;Janus spheres are then incorporated into electroactive polymers as fillers to enhance the electromechanical performance of acrylate polymer matrixes employing the fact that Janus spheres carry large dipole moments and orient themselves in an electric field. Incorporation of the electric-field aligned Au-caped sPS spheres increase the deformation strain of the tested acylate polymer dramatically from less than 10% to 80% and decreases the electric field required to below 20 V/mum.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Engineering
