title: Condensation and dissolution of nematic droplets in dispersions of colloidal rods with thermo-sensitive depletants.
abstract: Nematic droplets are droplets composed of elongated molecules that tend to point in the same direction but do not have any positional order. Such droplets are well known to adopt a spindle shape called tactoid. How such droplets condensate or melt and how the orientational symmetry is broken remains however unclear. Here we use a colloidal system composed of filamentous viruses as model rod-like colloids and pnipam microgel particles to induce thermo-sensitive depletion attraction between the rods. Microscopy experiments coupled to particle tracking reveal that the condensation of a nematic droplet is preceded by the formation of a new phase, an isotropic droplet. As the viruses constitute an excellent experimental realization of hard rods, it follows that the phenomenology we describe should be relevant to diverse micro- and nano-sized rods that interact through excluded volume interactions. This transition between isotropic and nematic droplets provides a new and reversible pathway to break the symmetry and order colloidal rods within a droplet with an external stimulus, and could constitute a benchmark experiment for a variety of technologies relying on reconfigurable control of rods.
authors.affiliation: Labaroire de physique, CNRS/UMR 5672, Ecole Normale Supérieure de Lyon - Université de Lyon, 46 allée d'Italie, 69007 Lyon, France.|Faculty of Technical Physics, Poznan University of Technology, ul. Piotrowo 3, 60-965 Poznań, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Modlińska
authors.affiliation: Complex Assemblies of Soft Matter (COMPASS), Solvay-CNRS-UPenn UMI 3254, Bristol, Pennsylvania 19007, USA.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Alsayed
authors.affiliation: Labaroire de physique, CNRS/UMR 5672, Ecole Normale Supérieure de Lyon - Université de Lyon, 46 allée d'Italie, 69007 Lyon, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gibaud