Polar interactions between bent–core molecules as a stabilising factor for inhomogeneous nematic phases with spontaneous bend deformations

M. A. Osipov, G. Pająk

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8 Citations (Scopus)

Abstract

It is generally accepted that the transition into the twist–bend nematic phase (NTB) is driven by an elastic instability related to the reduction of the bend elastic constant. Here we use a molecular–statistical theory to show that sufficiently strong polar interactions between bent–shaped molecules may lead to experimentally observed reduction of the bend elastic constant in the nematic phase even if electrostatic dipole-dipole interactions are not taken into account. We propose a simple model of bent–core particles and derive explicit analytical expressions which enable one to understand how polar molecular shape affects the elastic constants, and, in particular, the important role of the bend angle. Numerical graphs showing temperature variations of all elastic constants are also presented including the variation of the bend and splay elastic constants before and after the renormalization determined by local polar order of molecular steric dipoles and the corresponding polar correction to the one–particle distribution function.

LanguageEnglish
Pages58-67
Number of pages10
JournalLiquid Crystals
Volume44
Issue number1
Early online date3 Nov 2016
DOIs
Publication statusPublished - 5 Jan 2017

Fingerprint

Elastic constants
Elastic Constants
elastic properties
Molecules
Interaction
molecules
dipoles
Dipole
interactions
Distribution functions
Electrostatics
distribution functions
electrostatics
Twist
Renormalization
Distribution Function
Angle
Graph in graph theory
Temperature
temperature

Keywords

  • elasticity
  • liquid crystals
  • thermodynamics
  • analytical techniques
  • numerical techniques
  • twist-bend
  • nematics

Cite this

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abstract = "It is generally accepted that the transition into the twist–bend nematic phase (NTB) is driven by an elastic instability related to the reduction of the bend elastic constant. Here we use a molecular–statistical theory to show that sufficiently strong polar interactions between bent–shaped molecules may lead to experimentally observed reduction of the bend elastic constant in the nematic phase even if electrostatic dipole-dipole interactions are not taken into account. We propose a simple model of bent–core particles and derive explicit analytical expressions which enable one to understand how polar molecular shape affects the elastic constants, and, in particular, the important role of the bend angle. Numerical graphs showing temperature variations of all elastic constants are also presented including the variation of the bend and splay elastic constants before and after the renormalization determined by local polar order of molecular steric dipoles and the corresponding polar correction to the one–particle distribution function.",
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T1 - Polar interactions between bent–core molecules as a stabilising factor for inhomogeneous nematic phases with spontaneous bend deformations

AU - Osipov, M. A.

AU - Pająk, G.

N1 - The Version of Record of this manuscript has been published and is available in Liquid Crystals 03/11/2016 http://www.tandfonline.com/10.1080/02678292.2016.1247474

PY - 2017/1/5

Y1 - 2017/1/5

N2 - It is generally accepted that the transition into the twist–bend nematic phase (NTB) is driven by an elastic instability related to the reduction of the bend elastic constant. Here we use a molecular–statistical theory to show that sufficiently strong polar interactions between bent–shaped molecules may lead to experimentally observed reduction of the bend elastic constant in the nematic phase even if electrostatic dipole-dipole interactions are not taken into account. We propose a simple model of bent–core particles and derive explicit analytical expressions which enable one to understand how polar molecular shape affects the elastic constants, and, in particular, the important role of the bend angle. Numerical graphs showing temperature variations of all elastic constants are also presented including the variation of the bend and splay elastic constants before and after the renormalization determined by local polar order of molecular steric dipoles and the corresponding polar correction to the one–particle distribution function.

AB - It is generally accepted that the transition into the twist–bend nematic phase (NTB) is driven by an elastic instability related to the reduction of the bend elastic constant. Here we use a molecular–statistical theory to show that sufficiently strong polar interactions between bent–shaped molecules may lead to experimentally observed reduction of the bend elastic constant in the nematic phase even if electrostatic dipole-dipole interactions are not taken into account. We propose a simple model of bent–core particles and derive explicit analytical expressions which enable one to understand how polar molecular shape affects the elastic constants, and, in particular, the important role of the bend angle. Numerical graphs showing temperature variations of all elastic constants are also presented including the variation of the bend and splay elastic constants before and after the renormalization determined by local polar order of molecular steric dipoles and the corresponding polar correction to the one–particle distribution function.

KW - elasticity

KW - liquid crystals

KW - thermodynamics

KW - analytical techniques

KW - numerical techniques

KW - twist-bend

KW - nematics

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DO - 10.1080/02678292.2016.1247474

M3 - Article

VL - 44

SP - 58

EP - 67

JO - Liquid Crystals

T2 - Liquid Crystals

JF - Liquid Crystals

SN - 0267-8292

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ER -