Cluster self-organization of nanotubes in a nematic phase: The percolation behavior and appearance of optical singularities

Ponevchinsky, V. V.; Goncharuk, A. I.; Васильев, В. И.; Lebovka, Nikolaï; Soskin, M. S.

doi:10.1134/s0021364010050085

Cited by 29 publications

(39 citation statements)

References 7 publications

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“…Light shells near the surface of MWCNT aggregates observed in the external field clearly reflected strong anchoring of 5CB molecules to the surface of MWCNTs [28,29]. Strong anchoring of 5CB molecules to CNT walls [14,21] leads to complicated structure of aggregates consisting of 3d skeleton of nanotubes similar to that previously described in [52].…”

Section: The Responses On the Applied External Electric Fieldmentioning

confidence: 58%

“…The presence of CNTs perturbs the local ordering of a LC and results in formation of complex textures that can be detected by optical microscopy studies. The rich patterns of optical singularities were observed in nematic 5CB filled with CNTs, as reported in literature [28,29]. Many papers [30][31][32] contain explanatory drawings depicting CNT and NLC molecules in a joint supramolecular arrangement.…”

Section: Introductionmentioning

confidence: 86%

“…Strong tendency of CNTs for aggregation due to strong van der Waals interactions can affect significantly the structure of LC + CNT suspensions at higher concentrations of CNTs, and usually a thorough ultrasonication procedure is required for preparation of a more or less initially homogeneous LC + NTcomposite [36]. The aggregation aspects of CNTs in LC were measured and discussed [16,28,29,[36][37][38], though explicit data regarding concentration and time effects on the structure of LC + CNT suspensions are still absent and more studies in this field are needed.…”

Section: Introductionmentioning

confidence: 99%

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Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Lisetski

Minenko

Ponevchinsky

et al. 2011

Materialwissenschaft Werkst

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This work reports a study on microstructure, electrical conductivity and phase transitions of 5CB(4-pentyl-49-cyanobiphenyl) + multi-walled carbon nanotubes (MWCNTs) composite materials. The concentration of MWCNTs was varied within 0.025 and 1 wt.%. The unmodified (o) and modified (m) MWCNTs were used. The mild milling was applied for shortening length of MWCNTs. Direct microscopic observation of composites at different concentrations C of MWCNTs evidenced the presence of aggregation and percolation processes. Formation of percolation networks was observed at C p L 0.025 -0.05% wt and C=C p L 0.1 -0.25% wt for o-MWCNTs and m-MWCNTs composites, respectively. Increase of the percolation threshold for m-MWCNTs, possibly, reflected their smaller aspect ratio r. The conductivity exponents were approximately the same (t L 3.3 l 0.1) for both o-MWCNTs and m-MWCNTs. The microstructure of MWCNT aggregates was not stable in time. The initially formed loose aggregates (L-aggregates) transformed into the more compact C-aggregates during the incubation time of one week. The incubation resulted in decrease of anisotropy, change in phase behaviour near the nematic-isotropic transition, and influenced external electric field response of the studied composite material. Inkubation führt zu einer Abnahme der Anisotropie, einem Wechsel der Phase in der Nähe der nematischen-isotropen Umwandlung und beeinflusst die Antwort auf ein externes elektrisches Feld der studierten Kompositmaterialien.

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Section: The Responses On the Applied External Electric Fieldmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Lisetski

Minenko

Ponevchinsky

et al. 2011

Materialwissenschaft Werkst

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“…Clusters are enlarged with concentration grow up to formation of the percolation structure when all neighbor cluster touch [7,8,11]. This moment electrical conductivity enlarged nonlinearly on three-four orders [8].…”

Section: Lc Carbon Nanocompositesmentioning

confidence: 99%

“…The 'long'/'short' MWCNTs with 5÷10/1÷2 μm length were exploit. The first our measurements have shown that nanotubes form clusters [7,8]. The theory of CNT aggregation process was elaborated also [9].…”

Section: Lc Carbon Nanocompositesmentioning

confidence: 99%

Fine topological structure of coherent complex light created by carbon nanocomposites in LC

Ponevchinsky¹,

Goncharuk

Minenko

et al. 2012

SPIE Proceedings

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Fine complex light structure, optical singularities and electroconductivty of nematic 5CB doped by multi-walled carbon nanotubes (MWCNTs) were investigated. MWCNTs gather spontaneously to system of micro scale clusters with random fractal borders at small enough concentration. They are surrounded by the striped micro scale cladding which creates optical singularities in propagating laser beam. Applied transverse electric field above the Freedericksz initiates homeotropic arrangement of 5CB and the striped inversion walls between nanotubes clusters what diminishes free energy of a composite. Theory of their appearance and properties was built. Simultaneously the striped cladding disappears what can be treated as new mechanism of structure orientation nonlinearity in nonlinear photonics. Polarization singularities (circular C points) were measured firstly. Percolation of clusters enhances strongly electrical conductivity of the system and creates inversion walls even without applied field. Carbon nanotubes composites in LC form bridge between nano dopants and micro/macro system and are promising for applications. Elaborated protocol of singular optics inspection and characterization of LC nanocomposites is promising tool for applications in modern nanosience and technique.

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Liquid Crystals of Carbon Nanotubes and Carbon Nanotubes in Liquid Crystals

Scalia

2012

Liquid Crystals Beyond Displays

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Cluster self-organization of nanotubes in a nematic phase: The percolation behavior and appearance of optical singularities

Cited by 29 publications

References 7 publications

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Fine topological structure of coherent complex light created by carbon nanocomposites in LC

Liquid Crystals of Carbon Nanotubes and Carbon Nanotubes in Liquid Crystals

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