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ePaper created 2014-07-24, 14:56:51 | version 1.32.01
Janus particles are a new class of nanoparticles that show two different compartments on their surface. The anisotropic surface modification may result in different reactivity, polarity, or charges of the two surface sites. The surface-functionalization is carried out at the interphase of an emulsion stabilized by the nanoparticles. The setup offers three benefits: It provides two different environments, larger quantities of nanoparticles can be functionalized, and two compartments can be modified in a single step. In our primary project, metal oxide and silica particles will be functionalized in a Pickering emulsion (Fig. 1), using perfluorinated alkyl chains as modifiers for the surface-functionalization. Thus, we focus on the behavior of the modified particles in composite materials. We expect that the oil as well as water repellent fluorinated coating of the particles provide a driving force for self-assembly within the composite and especially on its surface. The modification of the SiO2 particles turned out to be a major chal- lenge due to their restrained reactivity towards alkoxysilane coupling agents usually applied. Therefore, it was necessary to “freeze” the particles on the interphase to allow long reaction periods. For this purpose, we used a liquid wax, which solidified with cooling to room temperature and kept the particles trapped on the interphase (Fig. 2). The modification of the trapped silica particles with perfluorinated surfactants is currently under investigation. Coupling agents with more reactive anchor groups are also used for surface-functionalization. Magnetite particles, which allow novel routes to switchable materials by external electromagnetic fields, are also under investigation. Contact: Prof. Dr. G. Kickelbick Saarland University Janus Nanoparticles Fig. 1: Preparation of Janus Nanoparticles in a Pickering emulsion. Fig. 2: REM image of the silica particles trapped on the surface of a wax. K. Abersfelder, P. W. de Oliveira, G. Kickelbick* 55Jahresbericht 2013 / Annual report 2013 * ) INM Fellow since 2013