Magnetic-Field-Induced Alignment and Instabilities in Ordered Colloids of Tobacco Mosaic Virus

Abstract

-Nous utilisons des champs magnétiques pour orienter des cristaux liquides nématiques ainsi que des solutions cristallines colloïdales monodisperses de virus du tabac (TMV). Les instabilités hydrodynamiques induites par les réorientations sous champ magnétique ont été étudiées sur des cristaux liquides nématiques bien orientés. Abstract-Magnetic fields have been used to produce well aligned nematic liquid crystalline and colloidal crystalline samples of nearly monodisperse tobacco mosaic virus (TMV). Hydrodynamic instabilities induced by reorientation in a magnetic field have been studied in the well aligned nematic liquid crystalline samples.

Isotropic−Nematic Phase Separation in Suspensions of Polydisperse Colloidal Platelets

“…Between φ ) 0.18 and φ ) 0.24, phase separation yields an isotropic upper phase and a nematic bottom phase ( Figure 3a); this is similar to other cases of I-N phase separation cited in the literature. 2,[4][5][6][7][8][9][10][11]14 However from φ ) 0.24 up to the completely nematic state, the nematic phase becomes the upper phase which coexists with an isotropic bottom phase ( Figure 3c). This implies that the nematic phase has a lower mass density than the coexisting isotropic phase.…”

“…Although Onsager's theoretical approach was inspired by experimental observations of I-N phase separation in suspensions of rodlike particles, 2 as well as suspensions of platelike colloids, 3 the presently known examples of I-N phase separating suspensions almost exclusively deal with particles of rodlike shape. 2,[4][5][6][7][8][9][10][11] In fact, Langmuir's observation of an I-N transition in suspensions of clay platelets (1938), 3 to which Onsager refers, later led to a contentious discussion as to why such suspensions more generally seem to form gels rather than to exhibit isotropic-nematic phase separation. 12,13 Recently, an alternative model system for platelike colloids has been developed, consisting of sterically stabilized gibbsite (Al(OH) 3 ) platelets.…”

Deformable homeotropic nematic droplets in a magnetic field

“…1,[3][4][5][6][7][8][9] Because the shape and structure of tactoids result in effect from a competition among surface, anchoring, and elastic forces, studying them provides quantitative information on material properties of liquid crystals, including the elastic constants, surface tension, and anchoring strength of the director field to the interface between the co-existing isotropic and nematic phases. 3,4,[6][7][8][9][10][11][12] Tactoids in lyotropic systems are more suitable for this purpose than those in thermotropics because of the extremely low surface free energies in lyotropics. [13][14][15] Studies on tactoids in dispersions of rod-like colloidal particles such as vanadium pentoxide, 1,3,4 f-actin, 5 tobacco mosaic virus, 16 boehmite, 17 and fd virus, 18 have shown that these drops tend to have a bipolar director field in which the curved field lines run from one virtual surface point defect (boojum) to another on the other side of the drop.…”

Linear Stability Analysis of One-Dimensional Models of Magneto-Hydrodynamic Domains in Nematics

“…Т. 15, № 3  Введение К настоящему времени экспериментально и теоретически изучены гидродинамические домены (ГД) двух видов, возникающие в нематических жидких кристаллах (НЖК) под действием магнитного поля -полосатые и паркетные [1][2][3][4][5][6]. Обе доменные структуры являются линиями вихря.…”