Glass Transition in Suspensions of Charged Rods: Structural Arrest and Texture Dynamics

Kang, Kyongok; Dhont, Jan K. G.

doi:10.1103/physrevlett.110.015901

Cited by 47 publications

(41 citation statements)

References 36 publications

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“…Kang and Dhont 46 reported the loss of equilibrium LC behavior for filamentous viruses beyond a critical volume fraction, yet this only happens at very low salt content. Their explanation was based on non-contact between the rods, in which the electrostatic repulsion is instead so effective at these low ion concentrations that the rods find themselves in an "electrostatic cage" if the particle volume fraction reaches a threshold value.…”

Section: >0mentioning

confidence: 99%

Fractionation of cellulose nanocrystals: enhancing liquid crystal ordering without promoting gelation

et al. 2018

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Colloids of electrically charged nanorods can spontaneously develop a fluid yet ordered liquid crystal phase, but this ordering competes with a tendency to form a gel of percolating rods. The threshold for ordering is reduced by increasing the rod aspect ratio, but the percolation threshold is also reduced with this change; hence, prediction of the outcome is nontrivial. Here, we show that by establishing the phase behavior of suspensions of cellulose nanocrystals (CNCs) fractionated according to length, an increased aspect ratio can strongly favor liquid crystallinity without necessarily influencing gelation. Gelation is instead triggered by increasing the counterion concentration until the CNCs lose colloidal stability, triggering linear aggregation, which promotes percolation regardless of the original rod aspect ratio. Our results shine new light on the competition between liquid crystal formation and gelation in nanoparticle suspensions and provide a path for enhanced control of CNC self-organization for applications in photonic crystal paper or advanced composites.

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Section: >0mentioning

confidence: 99%

Fractionation of cellulose nanocrystals: enhancing liquid crystal ordering without promoting gelation

et al. 2018

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“…Both processes are fast and take place in an otherwise barely moving collection of particles. In this sense, the dynamics is heterogeneous, i.e., glasslike [3,16].Before going into the details of the simulations, we present our experimental results. Fd viruses (contour length L ¼ 880 nm, diameter ¼ 6:6 nm, and persistence length P ¼ 2:8 m [17]) were prepared in aqueous solution having an ionic strength of 20 mM and a pH of 8.2 at a concentration of 130 mg=mL to obtain the columnar mesophase [7].…”

mentioning

confidence: 99%

“…Both processes are fast and take place in an otherwise barely moving collection of particles. In this sense, the dynamics is heterogeneous, i.e., glasslike [3,16].…”

mentioning

confidence: 99%

Fractional Hoppinglike Motion in Columnar Mesophases of Semiflexible Rodlike Particles

et al. 2013

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We report on single-particle dynamics of strongly interacting filamentous fd virus particles in the liquidcrystalline columnar state in aqueous solution. From fluorescence microscopy, we find that rare, discrete events take place, in which individual particles engage in sudden, jumplike motion along the main rod axis. The jump length distribution is bimodal and centered at half-and full-particle lengths. Our Brownian dynamics simulations of hard semiflexible particles mimic our experiments and indicate that full-length jumps must be due to collective dynamics in which particles move in stringlike fashion in and between neighboring columns, while half jumps arise as a result of particles moving into defects. We find that the finite domain structure of the columnar phase strongly influences the observed dynamics. The interplay between ordering, fluctuations, and mobility of particles is a key ingredient in our current understanding of soft matter. The Lindemann criterium for crystal melting purports that a crystal can only be stable provided that fluctuations of the particles away from the equilibrium positions are less than about 1=8 of the lattice distance [1], which indeed is observed in real space in crystalline dispersions of spherical colloids [2]. In glassy dispersions of colloidal spheres, there is no long-range order but particle caging hinders free diffusion: breaking and reformation of cages dominates the dynamics [3]. The situation is more complex for elongated colloidal particles such as DNA, actin filaments, and filamentous viruses because of the additional orientational degree of freedom [4,5]. This gives rise to a sequence of mesophases with increasing packing fraction, from the (chiral) nematic where there is only orientational ordering to smectic and (hexatic) columnar liquid-crystalline phases characterized by one-and two-dimensional positional order [6,7].While self-diffusion in nematic [8,9] and smectic [10-14] phases has been investigated theoretically and experimentally, little is known about dynamics in the dense columnar phase, where particles are stacked into liquidlike columns that are organized in a hexagonal array. Perfect hexagonal ordering is frustrated for the chiral fd virus by the helical twist of the particles, spawning dislocations. This breaks long-range hexagonal translational order, giving rise to a hexatic columnar phase [7]. In this Letter, we report on the intriguing motion of particles in this highly viscous hexatic phase, using particle tracking of fluorescently labeled fd viruses. We observe rare and discrete jump events along the director, predominantly of half a particle length, while a significant fraction of events involves full-length jumps. A small fraction of the particles reorients during the jump, hinting at the presence of structural defects, such as dislocations or grain boundaries.Hoppinglike diffusion processes of one rod length have been observed before in the smectic of an fd virus [11,12]. It stems from the underlying lamellar structure of the smectic th...

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“…The same experimental methods are used for long waiting time observation. Figure 5 depicts the initial break up of shear-aligned birefringent domains, after filling the cuvette, and the equilibration up to long waiting times, 80 -100 h, confirmed by an image-time correlation [7] [8]. Here a commercially available cylindrical cuvette (diameter of 20 mm and thickness 1 mm) is used and placed between the crossed polarizers.…”

Section: Glass Transition In Concentrationmentioning

confidence: 99%

“…Without an external electric field, at higher concentrations, a glass transition occurs far above the two-phase isotropic-nematic coexistence regions [7] [8]. Dynamic light scattering experiments will be discussed which reveal particle arrest, while image-time correlation shows freezing of the orientation texture dynamics, at the same concentration.…”

Section: Introductionmentioning

confidence: 99%

Charged Colloidal Rods Out of Equilibrium

Kang¹

2015

ACES

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This article is a comprehensive overview of the ongoing research of the author on charged colloidal rods out of equilibrium, under external electric fields and at high concentrations around the glass transition. The suspensions of fd-virus particles are used as a model system for charged colloidal rods, which exhibit several disorder-order (and liquid-crystalline) phase transitions. When a low AC electric field is applied to suspensions in isotropic-nematic coexistence concentration, with frequencies that are sufficiently low to polarize the electric double layer and the layer of condensed ions, various phases/states are induced: a chiral nematic, a dynamical state where nematic domains persistently melt and form, and a uniform homeotropic phase. A point in the field-amplitude versus frequency diagram, where various transitions lines meet, can be identified as a non-equilibrium critical point. Without an electric field, at high concentrations of charged fd-rods, various self-assembled orientation textures are found beyond the isotropic-nematic coexistence regions, and a glass transition is observed on approach and within the glass state that are probed. The presented system exhibits transient behaviors of repulsive glasses and slow dynamics out of equilibrium.

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Glass Transition in Suspensions of Charged Rods: Structural Arrest and Texture Dynamics

Cited by 47 publications

References 36 publications

Fractionation of cellulose nanocrystals: enhancing liquid crystal ordering without promoting gelation

Fractionation of cellulose nanocrystals: enhancing liquid crystal ordering without promoting gelation

Fractional Hoppinglike Motion in Columnar Mesophases of Semiflexible Rodlike Particles

Charged Colloidal Rods Out of Equilibrium

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