title: Experimental realization of crossover in shape and director field of nematic tactoids.
abstract: Spindle-shaped nematic droplets (tactoids) form in solutions of rod-like molecules at the onset of the liquid crystalline phase. Their unique shape and internal structure result from the interplay of the elastic deformation of the nematic and anisotropic surface forces. The balance of these forces dictates that tactoids must display a continuous variation in aspect ratio and director-field configuration. Yet, such continuous transition has eluded observation for decades: tactoids have displayed either a bipolar configuration with particles aligned parallel to the droplet interface or a homogeneous configuration with particles aligned parallel to the long axis of the tactoid. Here, we report the first observation of the continuous transition in shape and director-field configuration of tactoids in true solutions of carbon nanotubes in chlorosulfonic acid. This observation is possible because the exceptional length of carbon nanotubes shifts the transition to a size range that can be visualized by optical microscopy. Polarization micrographs yield the interfacial and elastic properties of the system. Absorbance anisotropy measurements provide the highest nematic order parameter (S=0.79) measured to date for a nematic phase of carbon nanotubes at coexistence with its isotropic phase.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.
authors.forename: Vida
authors.initials: V
authors.lastname: Jamali
authors.affiliation: Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.
authors.forename: Natnael
authors.initials: N
authors.lastname: Behabtu
authors.affiliation: Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.|Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
authors.forename: Bohdan
authors.initials: B
authors.lastname: Senyuk
authors.affiliation: Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.
authors.forename: J Alex
authors.initials: JA
authors.lastname: Lee
authors.affiliation: Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA.|Department of Electrical, Computer, and Energy Engineering and Materials Science and Engineering Program, and Liquid Crystals Materials Research Center, University of Colorado at Boulder, Colorado 80309, USA.|Renewable and Sustainable Energy Institute, National Renewable Energy Laboratory and University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: Ivan I
authors.initials: II
authors.lastname: Smalyukh
authors.affiliation: Polymer Physics Group for Theory of Polymers and Soft Matter Group, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.|Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: van der Schoot
authors.affiliation: Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.|Department of Chemistry, Department of Materials Science and NanoEngineering, The Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, Texas 77005, USA.
authors.forename: Matteo
authors.initials: M
authors.lastname: Pasquali