Kurzbeschreibung
(Englisch)
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The overall aim of this project is to develop a strategy for the synthesis of electrosterically stabilized rod-like magnetic (hematite) nanoparticles, and to investigate their self-assembly into highly ordered photonic crystals. The possibilities for surface functionalization of the bare magnetic nanoparticles with an organic polymer grafted on their surface are quite limited; therefore, the particles are first coated with a thin layer of silica in order to facilitate the subsequent attachment of a polymer initiator on their surface. Control of the initiator and monomer concentration will allow us to tailor the grafting density and chain length of the polyelectrolytes, which subsequently control the repulsive interactions between the particles. Moreover, we have already successfully established means to remove the magnetic core and thus produce rod-like hollow silica shells that interact via excluded volume interactions only. These model systems will thus allow us to investigate the influence of a non-centrosymmetric contribution to the interaction potential that can be either of pure excluded volume type for the silica shells or of soft long-range nature in the case of the magnetic particles on the phase behavior (crystallization and glass formation) of colloidal particles. Moreover, these particles will also be used in order to synthesize polymer-colloid nanocomposites via in-situ polymerization, where the particles can be oriented with an externally applied magnetic field and thus provide means to tune the mechanical, magnetic and optical properties of the resulting hybrid materials.
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Partner und Internationale Organisationen
(Englisch)
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AT, BG, CH, CY, CZ, DE, ES, FI, FR, GR, HR, HU, IE, IL, IT, LT, LV, NL, NO, PL, PT, RO, RS, SE, SI, SK, TR, UK
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Abstract
(Englisch)
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The overall aim of this project is to develop a strategy for the synthesis of electrosterically stabilized rod-like magnetic (hematite) nanoparticles, and to investigate their self-assembly into highly ordered photonic crystals. During this project, we have successfully synthesized different types of highly charged and electrosterically stabilized magnetic core-shell particles. These are based on a well defined and quite monodisperse core formed by hematite ellipsoids (200-500 nm length and axial ratios of 2-5), a silica shell and then either an irreversible grafted layer of poly acrylic acid or a theromresponsive PNIPAM microgel. Given the limited strength of the magnetic dipole moment that can be achieved with hematite, we have also extended the work to magnetic cores based on maghemite. These particles have been used to explore new routes to photonic crystals with added responsiveness. We have successfully tested the use of a PNIPAM-based shell in order to obtain large photonic crystals through temperature-induced annealing. We have also prepared nanocomposites using magnetic core-shell particles in order to create nanocomposite materials with improved mechanical properties and adjustable anisotropic magnetic properties.
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