We recently developed a way to synthesis bullet shaped fluorescent silica rods with aspect ratios as large as 10 [1]. It is possible to obtain both (absolute) orientations and positions of these new model particles even in concentrated systems with confocal microscopy. The rods can be made to interact with an almost hard potential in which case they form smectic and nematic liquid crystals phases that were studied in real space and by x-ray scattering [2]. By using an external electric field, the orientation of the LC and crystal phases could be improved at lower field strengths. At higher values dipolar interactions induced a new type of tetragonal crystal phase. When the double layer extends beyond the length of the rod we found in an extensive parameter range plastic crystals were long ranged positional order is combined with short-ranged rotational order. The plastic crystals could be switched into a fully crystalline state by application of an electric field. For higher volume fractions we also observed 'plastic glasses' for which positional order was short-ranged and translational self-diffusion was absent, while rotational diffusion was still possible. Also this phase could reversibly switched to a full 3D crystalline state with an electric field. This new model system will allow investigating the role of rotations in both crystallization and the glass transition and will also be of interest for new photonic applications. Finally, we will show that the directed growth of PMMA on the flat end of the silica bullets is possible with 100% yield, giving the possibility to further extend the anisotropy in the particle properties.1) A. Kuijk, A. Imhof, A. van Blaaderen, Journal of the American Chemical Society 133 , 2346 (2011)2) A. Kuijk, D. V. Byelov, A. V. Petukhov, A. van Blaaderen, A. Imhof, Faraday Discussions 159 , 181 (2012)

Bullet shaped fluorescent silica rods: New possibilities for synthesis and self-assembly

246th National Meeting (2013)

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