Résumé:

In a seminal paper, [1] D. R. Nelson proposed that a nematic coating could be used to promote localized functionalization on spheres by attaching ligands to the defects that necessarily arise in spherical nematics. However, using liquid crystals defects to fabricate novel colloids and novel forms of self-organization at the micron scale is still, to date, an experimental challenge. In this work, we have studied the properties of a simple experimental system which consists of micron-sized particles trapped on nematic shells. We especially have examined how the beads interact with the topological defects, where they get trapped, and how they are at the origin of new textures. We used water/5CB/water double emulsions produced by microfluidics technics. Nematic shells with a planar arrangement are obtained when PVA is added in the aqueous solutions [2]. The colloids are silica beads treated to provide a homeotropic alignment. Figure 1. Examples of textures observed in nematic shells in the presence of colloidal particles. In these shells, we observe various defect structures and patterns, different from the ones observed in simple nematic shells. We will describe their main features and explain how they result from the competition between elasticity and capillarity effects, during the formation of the shells. We will show how this last mechanism, among others [3], can be used to control the position of the ligands on the shell. References: [1] D.R. Nelson, Toward a Tetravalent Chemistry of Colloids, Nanoletters, 2, 1125 (2002). [2] T. Lopez-Leon,V. Koning, K. B. S. Devaiah, V. Vitelli and A. Fernandez-Nieves, Frustrated nematic order in spherical geometries, Nature Physics, 7 391 (2011). [3] T. Lopez-Leon, A. Fernandez-Nieves, M. Nobili and C. Blanc, Nematic-Smectic Transition in Spherical Shells, Phys. Rev. Lett. 106, 247802 (2011). _____________________________________________ * presenting author; E-mail: christophe.blanc02@univ-montp2.fr