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Hierarchical organization in liquid crystal-in-liquid crystal emulsions.

ABSTRACT: We report the formation and characterization of hierarchical ordering in systems comprised of micrometer-sized droplets of thermotropic nematic liquid crystals (LCs) dispersed in continuous nematic phases of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). Significantly, we find the orientations of the two LC phases to be coupled, with nematic droplets of 4'-pentyl-4-cyanobiphenyl (5CB) exhibiting a bipolar configuration with an axis of symmetry aligned orthogonal to the far-field director of the DSCG phase. We determine that this coupling of orientations does not result from either anisometric LC droplet shape or interfacial ionic phenomena but rather is consistent with the influence of van der Waals interactions that arise from the anisotropic polarizabilities of nematic 5CB (?n = +0.18) and DSCG (?n = -0.02) phases. We also find that it is possible to rotate and uniformly align the nematic droplets by using a weak magnetic field (B ? 0.3 T). An analysis of the dynamics of relaxation of the orientations of the 5CB droplets following removal of the magnetic field reveals the DSCG and 5CB droplets to be coupled by energies of ?10(4) kT, consistent with a simple theoretical estimate of the influence of anisotropic van der Waals interactions. We also observed the nematic 5CB droplets to form dimers and larger assemblies mediated by the elasticity of the nematic DSCG. Overall, these results reveal that LC-in-LC emulsions define a new class of hierarchically ordered soft matter in which both thermotropic and lyotropic LCs are coupled in their ordering.

SUBMITTER: Mushenheim PC

PROVIDER: S-EPMC4241356 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Hierarchical organization in liquid crystal-in-liquid crystal emulsions.

Mushenheim Peter C PC Abbott Nicholas L NL

Soft matter 20141101 43

We report the formation and characterization of hierarchical ordering in systems comprised of micrometer-sized droplets of thermotropic nematic liquid crystals (LCs) dispersed in continuous nematic phases of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). Significantly, we find the orientations of the two LC phases to be coupled, with nematic droplets of 4'-pentyl-4-cyanobiphenyl (5CB) exhibiting a bipolar configuration with an axis of symmetry aligned orthogonal to the far-field direct ...[more]

PMID: 25278032

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Project description:Liquid-infused membranes have been introduced to membrane technology recently. The infusion liquid can be expelled, opening the pore, in response to an immiscible feed liquid pressure. In the open state, the pore wall is still covered with the infusion liquid forming the so-called liquid-lined pores. Liquid lining is expected to give anti-fouling properties to these membranes. The pressure-responsive pores can be used for efficient sorting of fluids from a mixture based on interfacial tension. For example, in a two-phase mixture of immiscible liquids, the required liquid entry pressure is different for the constituent liquids. Here, we investigate the capability of liquid-infused membranes for selective permeation of the dispersed phase, that is, oil from an oil-in-water (O/W) emulsion. The separation experiments are conducted in a dead-end pressure-controlled filtration cell using liquid-infused and non-infused membranes. In order to permeate the dispersed phase, oil droplets should come in contact with the membrane surface which is accomplished here by gravity-driven creaming. Our results reveal that by setting the feed pressure between the entry pressure of oil and that of the surfactant solution, oil can be successfully permeated. For high concentrations of surfactants, water also permeated partly. The amount of water permeated through liquid-infused membranes is lower than that through non-infused membranes, caused by the corresponding interfacial tensions. The results suggest that the presence of the infusion liquid in the membrane gives rise to the formation of three-phase interfaces in the pore, namely, the interface between surfactant solution-oil (?12) and that between oil-infusion liquid (?23). Based on the interfacial energy contributions, the additional interface between oil and the infusion liquid gives rise to an increase in the liquid entry pressure for the surfactant solution based on the combined interfacial tension (?12 + ?23) leading to less water permeation.

Dataset Information

Hierarchical organization in liquid crystal-in-liquid crystal emulsions.

Publications

Hierarchical organization in liquid crystal-in-liquid crystal emulsions.

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