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Action of fields on captive disclination loops.

Mallory Dazza1,2, Rui Cabeça3, Simon Čopar4

  • 1Laboratoire de Physique des Solides, Université Paris-Sud, Bât. 510, 91405, Orsay, France.

The European Physical Journal. E, Soft Matter
|March 18, 2017
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Magnetic fields induce movement and rotation in disclination loops on polymeric fibers within nematics. This study reveals how field orientation and fiber anchoring control these dynamic effects, offering a new model for their behavior.

Keywords:
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Area of Science:

  • Physics
  • Materials Science
  • Polymer Science

Background:

  • Disclination loops are topological defects in liquid crystals.
  • Polymeric fibers can influence the behavior of liquid crystal phases.
  • External fields (electric, magnetic) can manipulate liquid crystal properties.

Purpose of the Study:

  • To investigate the effects of magnetic fields on disclination loops on polymeric fibers in nematics.
  • To characterize the translation and rotation of disclination loops under different field conditions.
  • To propose a theoretical model explaining the observed phenomena.

Main Methods:

  • Experimental observation of disclination loops on fibers in nematic liquid crystals.
  • Application of oblique and orthogonal magnetic fields.
  • Analysis of disclination loop translation and rotation.
  • Development of a theoretical model.

Main Results:

  • Oblique magnetic fields induce translation of disclination loops.
  • Orthogonal magnetic fields cause disclination loops to rotate.
  • The rotation angle is proportional to the helix wave vector and indicates helix chirality.
  • A model was proposed to explain these effects.

Conclusions:

  • Magnetic fields provide a controllable method to manipulate disclination loops on fibers in nematics.
  • The observed effects are dependent on the orientation of the magnetic field and the fiber's anchoring.
  • The proposed model successfully explains the translation and rotation behaviors, including the chirogyral effect.