Résumé:

In many aspects, colloids behave as big atoms [1]; however, the usual absence of directionality in the interaction between colloids has limited the complexity of the structures that they can spontaneously form [2]. As a result, low-coordination structures, common in atomic and molecular systems, are rare in the colloidal domain. One way to address this is to exploit the anisotropy that spontaneously arises when a colloidal particle is coated by a nematic liquid crystal. In this spherical geometry, the orientational molecular order of the nematic liquid crystal is disrupted by the presence of singularities or topological defects, which appear symmetrically organized on the particle surface. These topological defects are not only mathematic concepts, but also high energy spots suitable for chemical attack that could be functionalized with ligands and act as attractive patches between particles [3,4]. The number and arrangement of these defects can vary, providing flexibility for tuning directional interactions. We have recently shown that these defects can be engineered to emulate the linear, trigonal and tetrahedral geometries of sp, sp2, and sp3carbon bonds [5]. These symmetries represent just a small sample of the variety of configurations that we can generate by tuning parameters such as shell geometry, temperature, or symmetry of the liquid crystal phase, which has revealed a vast playground for the formation of complex colloidal superlattices [5,6].