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Related Concept Videos

Thermal Sigmatropic Reactions: Overview01:16

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Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in 1,5-hexadiene, referred to as...
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Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
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Published on: May 15, 2017

Nematic-smectic transition in spherical shells.

Teresa Lopez-Leon1, Alberto Fernandez-Nieves, Maurizio Nobili

  • 1Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, Montpellier, France. Teresa.Lopez-Leon@univ-montp2.fr

Physical Review Letters
|July 21, 2011
PubMed
Summary
This summary is machine-generated.

Confined liquid crystals near the nematic-smectic transition exhibit four +1/2 defects. Near the transition temperature, these defects shift to a great circle, forming pairs, and a new smectic phase configuration appears.

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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Published on: June 7, 2018

Area of Science:

  • Soft Matter Physics
  • Liquid Crystal Science
  • Materials Science

Background:

  • Thermotropic liquid crystals exhibit various mesophases, including nematic and smectic phases.
  • Confining liquid crystals to curved geometries, like spherical shells, can alter their phase behavior and defect structures.
  • Understanding phase transitions and defect dynamics is crucial for liquid crystal applications.

Purpose of the Study:

  • To investigate the nematic-smectic phase transition of a thermotropic liquid crystal within a spherical shell geometry.
  • To analyze the behavior and arrangement of topological defects (+1/2 defects) during this transition.
  • To identify novel configurations in the smectic phase.

Main Methods:

  • Experimental observation of liquid crystal confinement in a spherical shell.
  • Varying temperature to induce the nematic-smectic phase transition.
  • Microscopic analysis of defect structures and their evolution.

Main Results:

  • Observed four +1/2 defects far from the transition temperature, localized at the thinnest shell region.
  • Near the nematic-smectic transition temperature, defects rearranged along a great circle, forming two independent pairs.
  • A new configuration with curvature walls was identified in the smectic phase.

Conclusions:

  • The study confirms theoretical predictions regarding defect behavior in confined liquid crystals.
  • The anisotropic elastic constants (K(1) and K(3)) significantly influence defect organization near the phase transition.
  • The observed curvature walls represent a novel structural feature in the smectic phase of confined liquid crystals.