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Colloidal templating at a cholesteric-oil interface: assembly guided by an array of disclination lines
J S Lintuvuori1, A C Pawsey, K Stratford
1SUPA, School of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom.
Physical Review Letters
|May 21, 2013
Summary
Colloids trapped at liquid crystal-oil interfaces form ordered arrays of defects. Particle positions depend on their size relative to the liquid crystal pitch, but this templating disappears at larger sizes due to complex defect interactions.
Area of Science:
- Soft matter physics
- Colloid science
- Liquid crystals
Background:
- Cholesteric liquid crystals exhibit helical structures.
- Interfaces between liquid crystals and immiscible oils can stabilize topological defects.
- Colloids at interfaces can influence or be influenced by interfacial phenomena.
Purpose of the Study:
- To investigate the self-assembly of colloidal particles at a cholesteric liquid crystal-oil interface.
- To understand how the interplay between helical pitch and particle size affects particle ordering.
- To explore the role of surface anchoring strength in colloidal self-organization.
Main Methods:
- Numerical simulations of colloidal particles at a liquid crystal-oil interface.
- Theoretical analysis of director field orientation and defect formation.
- Optical microscopy experiments to observe particle arrangements.
Main Results:
- Simulations and experiments show that colloids form ordered arrays of disclinations at the interface.
- Particle positions are templated by defect lines, with favored locations depending on the ratio of particle radius (R) to helical pitch (p), denoted as α=R/p.
- For small α, experimental results align with simulations, but for larger α, templating is not observed.
- A rugged energy landscape due to defect reconnections may explain the loss of templating at larger α and moderate anchoring strength (W).
Conclusions:
- Colloidal particle size relative to the liquid crystal pitch dictates self-assembly behavior at interfaces.
- The transition from ordered templating to disordered arrangements is linked to complex defect dynamics.
- Understanding these interactions is crucial for designing novel colloidal structures and materials.
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