Nematic liquid crystals doped with nanoparticles: phase behavior and dielectric properties

Mikhail A. Osipov, Maxim V. Gorkounov

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

Thermodynamics and dielectric properties of nematic liquid crystals doped with various nanoparticles have been studied in the framework of a molecular mean-field theory. It is shown that spherically isotropic nanoparticles efectively dilute the liquid crystal material and cause a de- crease of the nematic-isotropic transition temperature, while anisotropic nanoparticles are aligned by the nematic host and, in turn, may sig- nifcantly improve the liquid crystal alignment. In the case of strong interaction between spherical nanoparticles and mesogenic molecules, the nanocomposite possesses a number of unexpected properties: The nematic-isotropic co-existence region appears to be very broad, and the system either undergoes a direct transition from the isotropic phase into the phase-separated state, or undergoes first a transition into the ho- mogeneous nematic phase and then phase-separates at a lower tempera- ture. The phase separation does not occur for sufficiently low nanopar- ticle concentrations, and, in certain cases, the separation takes place only within a finite region of the nanoparticle concentration. For ne- matics doped with strongly polar nanoparticles, the theory predicts the nanoparticle aggregation in linear chains that make a substantial contri- bution to the static dielectric anisotropy and optical birefringence of the nematic composite. The theory clarifies the microscopic origin of im- portant phenomena observed in nematic composites including a shift of the isotropic-nematic phase transition and improvement of the nematic order; a considerable softening of the first order nematic-isotropic tran- sition; a complex phase-separation behavior; and a significant increase of the dielectric anisotropy and the birefringence.
LanguageEnglish
Title of host publicationLiquid Crystals with Nano and Microparticles
EditorsJan P F Lagerwall, Giusy Scalia
Place of PublicationSingapore
Number of pages41
DOIs
Publication statusPublished - 31 Oct 2016

Publication series

NameSeries in Soft Condensed Matter
PublisherWorld Scientific
Volume7

Fingerprint

Nematic liquid crystals
Phase behavior
Dielectric properties
Nanoparticles
Liquid Crystals
Birefringence
Phase separation
Anisotropy
Mean field theory
Composite materials
Nanocomposites
Thermodynamic properties
Agglomeration
Phase transitions
Molecules

Keywords

  • liquid crystals
  • colloidal crystals
  • nanoparticles

Cite this

Osipov, M. A., & Gorkounov, M. V. (2016). Nematic liquid crystals doped with nanoparticles: phase behavior and dielectric properties. In J. P. F. Lagerwall, & G. Scalia (Eds.), Liquid Crystals with Nano and Microparticles (Series in Soft Condensed Matter; Vol. 7). Singapore. https://doi.org/10.1142/9280
Osipov, Mikhail A. ; Gorkounov, Maxim V. / Nematic liquid crystals doped with nanoparticles : phase behavior and dielectric properties. Liquid Crystals with Nano and Microparticles. editor / Jan P F Lagerwall ; Giusy Scalia. Singapore, 2016. (Series in Soft Condensed Matter).
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abstract = "Thermodynamics and dielectric properties of nematic liquid crystals doped with various nanoparticles have been studied in the framework of a molecular mean-field theory. It is shown that spherically isotropic nanoparticles efectively dilute the liquid crystal material and cause a de- crease of the nematic-isotropic transition temperature, while anisotropic nanoparticles are aligned by the nematic host and, in turn, may sig- nifcantly improve the liquid crystal alignment. In the case of strong interaction between spherical nanoparticles and mesogenic molecules, the nanocomposite possesses a number of unexpected properties: The nematic-isotropic co-existence region appears to be very broad, and the system either undergoes a direct transition from the isotropic phase into the phase-separated state, or undergoes first a transition into the ho- mogeneous nematic phase and then phase-separates at a lower tempera- ture. The phase separation does not occur for sufficiently low nanopar- ticle concentrations, and, in certain cases, the separation takes place only within a finite region of the nanoparticle concentration. For ne- matics doped with strongly polar nanoparticles, the theory predicts the nanoparticle aggregation in linear chains that make a substantial contri- bution to the static dielectric anisotropy and optical birefringence of the nematic composite. The theory clarifies the microscopic origin of im- portant phenomena observed in nematic composites including a shift of the isotropic-nematic phase transition and improvement of the nematic order; a considerable softening of the first order nematic-isotropic tran- sition; a complex phase-separation behavior; and a significant increase of the dielectric anisotropy and the birefringence.",
keywords = "liquid crystals, colloidal crystals, nanoparticles",
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Osipov, MA & Gorkounov, MV 2016, Nematic liquid crystals doped with nanoparticles: phase behavior and dielectric properties. in JPF Lagerwall & G Scalia (eds), Liquid Crystals with Nano and Microparticles. Series in Soft Condensed Matter, vol. 7, Singapore. https://doi.org/10.1142/9280

Nematic liquid crystals doped with nanoparticles : phase behavior and dielectric properties. / Osipov, Mikhail A.; Gorkounov, Maxim V.

Liquid Crystals with Nano and Microparticles. ed. / Jan P F Lagerwall; Giusy Scalia. Singapore, 2016. (Series in Soft Condensed Matter; Vol. 7).

Research output: Chapter in Book/Report/Conference proceedingChapter

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T1 - Nematic liquid crystals doped with nanoparticles

T2 - phase behavior and dielectric properties

AU - Osipov, Mikhail A.

AU - Gorkounov, Maxim V.

N1 - Electronic version of an article published asOsipov, M. A., & Gorkounov, M. V. (2016). Nematic liquid crystals doped with nanoparticles: phase behavior and dielectric properties. In J. P. F. Lagerwall, & G. Scalia (Eds.), Liquid Crystals with Nano and Microparticles (Series in Soft Condensed Matter; Vol. 7). Singapore: World Scientific Publishing Company. DOI: 10.1142/9280 - © World Scientific Publishing Company.

PY - 2016/10/31

Y1 - 2016/10/31

N2 - Thermodynamics and dielectric properties of nematic liquid crystals doped with various nanoparticles have been studied in the framework of a molecular mean-field theory. It is shown that spherically isotropic nanoparticles efectively dilute the liquid crystal material and cause a de- crease of the nematic-isotropic transition temperature, while anisotropic nanoparticles are aligned by the nematic host and, in turn, may sig- nifcantly improve the liquid crystal alignment. In the case of strong interaction between spherical nanoparticles and mesogenic molecules, the nanocomposite possesses a number of unexpected properties: The nematic-isotropic co-existence region appears to be very broad, and the system either undergoes a direct transition from the isotropic phase into the phase-separated state, or undergoes first a transition into the ho- mogeneous nematic phase and then phase-separates at a lower tempera- ture. The phase separation does not occur for sufficiently low nanopar- ticle concentrations, and, in certain cases, the separation takes place only within a finite region of the nanoparticle concentration. For ne- matics doped with strongly polar nanoparticles, the theory predicts the nanoparticle aggregation in linear chains that make a substantial contri- bution to the static dielectric anisotropy and optical birefringence of the nematic composite. The theory clarifies the microscopic origin of im- portant phenomena observed in nematic composites including a shift of the isotropic-nematic phase transition and improvement of the nematic order; a considerable softening of the first order nematic-isotropic tran- sition; a complex phase-separation behavior; and a significant increase of the dielectric anisotropy and the birefringence.

AB - Thermodynamics and dielectric properties of nematic liquid crystals doped with various nanoparticles have been studied in the framework of a molecular mean-field theory. It is shown that spherically isotropic nanoparticles efectively dilute the liquid crystal material and cause a de- crease of the nematic-isotropic transition temperature, while anisotropic nanoparticles are aligned by the nematic host and, in turn, may sig- nifcantly improve the liquid crystal alignment. In the case of strong interaction between spherical nanoparticles and mesogenic molecules, the nanocomposite possesses a number of unexpected properties: The nematic-isotropic co-existence region appears to be very broad, and the system either undergoes a direct transition from the isotropic phase into the phase-separated state, or undergoes first a transition into the ho- mogeneous nematic phase and then phase-separates at a lower tempera- ture. The phase separation does not occur for sufficiently low nanopar- ticle concentrations, and, in certain cases, the separation takes place only within a finite region of the nanoparticle concentration. For ne- matics doped with strongly polar nanoparticles, the theory predicts the nanoparticle aggregation in linear chains that make a substantial contri- bution to the static dielectric anisotropy and optical birefringence of the nematic composite. The theory clarifies the microscopic origin of im- portant phenomena observed in nematic composites including a shift of the isotropic-nematic phase transition and improvement of the nematic order; a considerable softening of the first order nematic-isotropic tran- sition; a complex phase-separation behavior; and a significant increase of the dielectric anisotropy and the birefringence.

KW - liquid crystals

KW - colloidal crystals

KW - nanoparticles

UR - http://www.worldscientific.com/worldscibooks/10.1142/9280

U2 - 10.1142/9280

DO - 10.1142/9280

M3 - Chapter

SN - 9789814619257

T3 - Series in Soft Condensed Matter

BT - Liquid Crystals with Nano and Microparticles

A2 - Lagerwall, Jan P F

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Osipov MA, Gorkounov MV. Nematic liquid crystals doped with nanoparticles: phase behavior and dielectric properties. In Lagerwall JPF, Scalia G, editors, Liquid Crystals with Nano and Microparticles. Singapore. 2016. (Series in Soft Condensed Matter). https://doi.org/10.1142/9280