Liquid crystalline superatoms

Orateur : Teresa LOPEZ-LEON (UMR Gulliver CNRS-ESPCI, Paris)

Liquid crystals exhibit fascinating behaviors when confined to spaces with spherical curvature, due to the impossibility of establishing their preferential orientational molecular order everywhere in space. One of the most outstanding consequences is the presence of topological defects in their ground states. The number and distribution of defects depend on a fine interplay between topology and energy : while topology dictates certain broad features of the defect structure, energy controls the detailed structure of the liquid crystal. Spherical nematics have enormous potential not only from a fundamental point of view but also from a technological perspective, since defects may be functionalized with ligands that would direct the interactions between shells. In this way, nano- to meso- scale superatoms may be designed with specific valency for use in building supermolecules and novel bulk materials. In this talk, I will show recent advances in the field. Microfluidic techniques have allowed the experimental realization of nematic shells. A precise control in the defect architecture has been achieved by tuning parameters such as shell thickness, anchoring of the liquid crystal at the boundaries, or the type of liquid crystal phase considered. A number of different defect structures have been engineered, including the sp, sp2 and sp3 symmetries of carbon atoms, which has revealed a promising playground for the formation of colloidal super-lattices with potential applications in photonics.

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