A Self-Quenched Defect Glass in a Colloid-Nematic Liquid Crystal Composite

Wood, Tiffany; Lintuvuori, Juho S.; Schofield, Andrew B.; Marenduzzo, Davide; Poon, Wilson

doi:10.1126/science.1209997

Cited by 151 publications

(166 citation statements)

References 39 publications

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“…Large NPs perturbed the Ch director around them and exhibited attraction through long-range elastic forces (31,32). In addition, these NP clusters did not relax their irregular shape to equilibrium shape, due to large (compared with thermal energy) energy barriers (33).…”

Section: Resultsmentioning

confidence: 99%

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Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Prince

Cho

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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An important goal of the modern soft matter science is to discover new self-assembly modalities to precisely control the placement of small particles in space. Spatial inhomogeneity of liquid crystals offers the capability to organize colloids in certain regions such as the cores of the topological defects. Here we report two selfassembly modes of nanoparticles in linear defects-disclinations in a lyotropic colloidal cholesteric liquid crystal: a continuous helicoidal thread and a periodic array of discrete beads. The beads form one-dimensional arrays with a periodicity that matches half a pitch of the cholesteric phase. The periodic assembly is governed by the anisotropic surface tension and elasticity at the interface of beads with the liquid crystal. This mode of self-assembly of nanoparticles in disclinations expands our ability to use topological defects in liquid crystals as templates for the organization of nanocolloids. colloidal liquid crystals | nanoparticle self-assembly | liquid crystal droplets | topological defects | anisotropic surface tension T he most extensively studied liquid crystalline phase, the socalled nematic, has been so named after the linear defectdisclinations that appear as flexible threads in optical microscopy textures; "thread" is "ν«μα" in Greek (1, 2). The disclinations represent singularities of the director that describes the local orientation of molecules. As one approaches the "core" of the defect, director deformation becomes so strong that the degree of orientational order varies in space. Disclinations can attract additives, e.g., colloidal particles (3-8) and even small molecules (9, 10). Such an attraction is energetically favored, as the strongly distorted disclination core region is replaced with the additive (4). The unique templating ability of disclinations has stimulated the exploration of their applications, such as the fabrication of optical materials (11), conductive microwires (12), soft magnets (13), and electrooptical devices (5,14,15).Disclinations in nematic liquid crystals are generally onedimensional structures, as the director pattern repeats itself along the line. When an additive is attracted to the disclination core, two possible morphologies are expected: (i) continuous thread-like assembly, or (ii) a linear array of discrete beads. The disclination-templated assemblies reported so far had a threadlike shape, as observed for polymers in the so-called blue phases (15) and for molecular amphiphiles at the cores of nematic disclinations (9, 10).Here, we report the templating behavior of disclinations in the chiral version of the nematic liquid crystal, the so-called cholesteric (Ch) phase. The local directorn in this phase undergoes helicoid twisting around a helical axisv while being perpendicular to this axis (1, 2). Continuous twist leads to a pseudolayered structure, with a well-defined pitch but no modulation of density. Experiments were performed for spherical Ch droplets, in which disclinations correspond to the equilibrium state, thus ensuring...

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Section: Resultsmentioning

confidence: 99%

“…Mediumsize 184-and 457-nm NPs distort the director and thus partition in the Ch-CNC droplet core and disclinations, where they exhibit the beading effect. Large 787-nm NPs form kinetically trapped irregularly shaped clusters in the Ch-CNC shells that do not relax into equilibrium shapes (33) and the effect of beading is not observed.…”

Section: Discussionmentioning

confidence: 99%

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Prince

Cho

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…At the same time it was generally understood from the basic symmetry considerations that the elastic interaction between colloidal particles is not limited to two dimensions. There were predictions 20 as well as experimental studies reporting the formation of irregular 3D colloidal clusters in nematic LCs 21,22 . Recently, computer simulations were used to study colloidal interactions and regular clusters in LCs in full three dimensions 23 .…”

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Assembly and control of 3D nematic dipolar colloidal crystals

et al. 2013

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Topology has long been considered as an abstract mathematical discipline with little connection to material science. Here we demonstrate that control over spatial and temporal positioning of topological defects allows for the design and assembly of three-dimensional nematic colloidal crystals, giving some unexpected material properties, such as giant electrostriction and collective electro-rotation. Using laser tweezers, we have assembled threedimensional colloidal crystals made up of 4 mm microspheres in a bulk nematic liquid crystal, implementing a step-by-step protocol, dictated by the orientation of point defects. The threedimensional colloidal crystals have tetragonal symmetry with antiparallel topological dipoles and exhibit giant electrostriction, shrinking by 25-30% at 0.37 V mm À 1 . An external electric field induces a reversible and controllable electro-rotation of the crystal as a whole, with the angle of rotation being B30°at 0.14 V mm À 1 , when using liquid crystal with negative dielectric anisotropy. This demonstrates a new class of electrically highly responsive soft materials.

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“…For instance, colloidal scientists and soft matter physicists have explored the feasibility of self-assemblying extended photonic crystals and other metamaterials by designing patchy particles of increasingly complex surface activity [1][2][3][4] , by exploiting the shape anisotropy of convex polyhedrical colloids 5,6 or by choosing to disperse particles into complex fluids such as binary fluids or liquid crystals [7][8][9][10] . The resulting interparticle interactions are in general highly non-trivial and can promote the formation of crystals, glasses, gels and so on, often with tunable physical properties 11 .…”

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confidence: 99%

Self-assembling knots of controlled topology by designing the geometry of patchy templates

et al. 2015

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The self-assembly of objects with a set of desired properties is a major goal of material science and physics. A particularly challenging problem is that of self-assembling structures with a target topology. Here we show by computer simulation that one may design the geometry of string-like rigid patchy templates to promote their efficient and reproducible self-assembly into a selected repertoire of non-planar closed folds including several knots. In particular, by controlling the template geometry, we can direct the assembly process so as to strongly favour the formation of constructs tied in trefoil or pentafoil, or even of more exotic torus knots. Polydisperse and racemic mixtures of helical fragments of variable composition add further tunability in the topological self-assembly we discovered. Our results should be relevant to the design of new ways to synthesize molecular knots, which may prove, for instance, to be efficient cargo-carriers due to their mechanical stability.

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A Self-Quenched Defect Glass in a Colloid-Nematic Liquid Crystal Composite

Cited by 151 publications

References 39 publications

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Assembly and control of 3D nematic dipolar colloidal crystals

Self-assembling knots of controlled topology by designing the geometry of patchy templates

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