Effective interactions of colloids on nematic films

Oettel, Martin; Domínguez, A.; Tasinkevych, M.; Dietrich, S.

doi:10.1140/epje/i2008-10360-1

Cited by 31 publications

(34 citation statements)

References 42 publications

(146 reference statements)

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“…The asymptotic analysis for similar hybrid boundary conditions (both assumed to be rigid) predicted a power-law decay of the expelling force of at least (R/h) 8 [121], which basically reflects the fact that stronger elastic deformations of the director field are created in thinner nematic films. It is clear from the insets of figure 9 that this scaling does not hold in our case.…”

Section: Single Particle At a Ni Interfacementioning

confidence: 83%

“…Note, however, that this might be an artifact of the assumption of the infinitely strong director anchoring at the particle surface, which results in stronger elastic deformations for thinner films. In addition, our calculations assume that the homeotropic anchoring at the NI interface is rather weak, contrary to infinitely strong homeotropic anchoring assumed in [121].…”

Section: Single Particle At a Ni Interfacementioning

confidence: 95%

“…Asymptotic analysis predicts that, for the case of homeotropic anchoring at the interface, the elastic interaction is quadrupolar, repulsive, and decays with the distance as (R/d) −5 [120,121]. Numerical calculations are also not straightforward because the interfacial width and the size of the defect core are normally much smaller that the size of a colloidal particle.…”

Section: Colloids At Interfacesmentioning

confidence: 99%

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Colloidal particles in liquid crystal films and at interfaces

Tasinkevych¹,

Andrienko²

2010

Condens. Matter Phys.

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This mini-review discusses the recent contribution of theoretical and computational physics as well as experimental efforts to the understanding of the behavior of colloidal particles in confined geometries and at liquid crystalline interfaces. Theoretical approaches used to study trapping, long-and short-range interactions, and assembly of solid particles and liquid inclusions are outlined. As an example, an interaction of a spherical colloidal particle with a nematic-isotropic interface and a pair interaction potential between two colloids at this interface are obtained by minimizing the Landau-de Gennes free energy functional using the finite-element method with adaptive meshes.

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Section: Single Particle At a Ni Interfacementioning

confidence: 83%

Section: Single Particle At a Ni Interfacementioning

confidence: 95%

Section: Colloids At Interfacesmentioning

confidence: 99%

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Colloidal particles in liquid crystal films and at interfaces

Tasinkevych¹,

Andrienko²

2010

Condens. Matter Phys.

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“…Past studies of the interactions of microdroplets confined at the interface of a LC have also found evidence of attractive interdroplet interactions (4)(5)(6)(7)(19)(20)(21)(22)(23). The attractive forces were initially attributed to a many-bodied "elastic-capillary" interaction between microdroplets (5,7,19,20).…”

Section: Resultsmentioning

confidence: 99%

“…The attractive forces were initially attributed to a many-bodied "elastic-capillary" interaction between microdroplets (5,7,19,20). More recently, however, the role of the elastic-capillary interaction has been questioned (4,22,23), and the attraction that stabilizes arrays of microdroplets has been proposed to be because of "genuine many-body effects" (22) and a universal collective attraction of clusters of microdroplets at interfaces that provides enhancement of up to 10 5 compared to pairwise attractions (23). Our observation that micro- particles at 5CB-aqueous interfaces form two-dimensional arrays stabilized by an attractive force (and correspondingly, regions void of particles), when combined with our observation of the absence of hexagonal arrays at low particle densities, is consistent with the presence of some type of many-bodied attractive interaction between the microparticles at this interface.…”

Section: Resultsmentioning

confidence: 99%

Chemoresponsive assemblies of microparticles at liquid crystalline interfaces

Koenig

Lin

Abbott

2010

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

108

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Assemblies formed by solid particles at interfaces have been widely studied because they serve as models of molecular phenomena, including molecular self-assembly. Solid particles adsorbed at interfaces also provide a means of stabilizing liquid-liquid emulsions and synthesizing materials with tunable mechanical, optical, or electronic properties. Whereas many past studies have investigated colloids at interfaces of isotropic liquids, recently, new types of intercolloidal interactions have been unmasked at interfaces of liquid crystals (LCs): The long-range ordering of the LCs, as well as defects within the LCs, mediates intercolloidal interactions with symmetries that differ from those observed with isotropic liquids. Herein, we report the decoration of interfaces formed between aqueous phases and nematic LCs with prescribed densities of solid, micrometer-sized particles. The microparticles assemble into chains with controlled interparticle spacing, consistent with the dipolar symmetry of the defects observed to form about each microparticle. Addition of a molecular surfactant to the aqueous phase results in a continuous ordering transition in the LC, which triggers reorganization of the microparticles, first by increasing the spacing between microparticles within chains and ultimately by forming two-dimensional arrays with local hexagonal symmetry. The ordering transition of the microparticles is reversible and is driven by surfactant-induced changes in the symmetry of the topological defects induced by the microparticles. These results demonstrate that the orderings of solid microparticles and molecular adsorbates are strongly coupled at the interfaces of LCs and that LCs offer the basis of methods for reversible, chemosensitive control of the interfacial organization of solid microparticles. colloidal interactions | interfacial assemblies | liquid crystals | ordering transitionsA liquid crystal (LC) is a phase of matter that blends properties that are typically associated with either crystalline solids or isotropic liquids (1). The molecules that comprise nematic LC phases exhibit long-range orientational order, yet they also possess mobilities characteristic of an isotropic liquid. LCs are most widely known for their use in electrooptic displays; however, they are increasingly being studied in the context of biology, materials science, and analytical chemistry (1). Recently, for example, microdroplets and microparticles dispersed in bulk LCs have been shown to form ordered assemblies, demonstrating that LCs can provide routes to stabilizing emulsions and assembling solid particles into colloidal crystals (2, 3). Although the origins of the interparticle forces that direct the formation of these assemblies in bulk LCs are not yet completely understood, it is clear that the long-range orientational ordering of molecules within the LC phase gives rise to interparticle forces that can be described in terms of the elasticity of the LCs and formation of topological defects within the LC. The LC-mediated interpart...

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