Sliding planar anchoring and viscous surface torque in a cholesteric liquid crystal

Patrick Oswald 1 Alain Dequidt 1 Andrzej Zywocinski 1, 2
1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 Institute of Physical Chemistry
Abstract : We propose a new surface treatment allowing to obtain a sliding planar anchoring of nematic (or cholesteric) liquid crystals. It consists of depositing a thin layer of the polymercaptan hardener of an epoxy resin on an isotropic substrate (bare or ITO-coated glass plates). Microscopic observations of defect annihilations and capacitance measurements show that the molecules align parallel to the surface and slide viscously on it when they change orientation, which implies a zero (or extremely small) azimuthal anchoring energy. By contrast, the zenithal anchoring energy W_\theta is found to be larger than 3\times10^{-5} J/m{^2}. We also measured the liquid crystal rotational surface viscosity \gamma_S by a new thermo-optical method using the large temperature variation of the pitch of a compensated cholesteric mixture. We found that the sliding length \gamma_S/\gamma_1 (where \gamma_1 is the bulk rotational viscosity) is very large in comparison with the length of a liquid crystal molecule. This result is explained by a simple model which takes into account the diffusion of the liquid crystal within the polymer layer.
Keywords : Nematic and cholesteric liquid crystals Sliding anchoring Surface viscosity
Document type :
Journal articles
Complete list of metadatas

Cited literature [27 references]  Display  Hide  Download
https://hal-ens-lyon.archives-ouvertes.fr/ensl-00351712
Contributor : Patrick Oswald <>
Submitted on : Saturday, January 10, 2009 - 7:12:39 PM
Last modification on : Wednesday, November 20, 2019 - 2:48:23 AM
Long-term archiving on: Thursday, October 11, 2012 - 3:43:24 PM

File

Osw-Deq-ZywoPRE08.pdf
Files produced by the author(s)

Identifiers

Collections

CNRS | ENS-LYON | UNIV-LYON1 | UDL

Citation

Patrick Oswald, Alain Dequidt, Andrzej Zywocinski. Sliding planar anchoring and viscous surface torque in a cholesteric liquid crystal. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2008, 77 (6), pp.061703. ⟨10.1103/PhysRevE.77.061703⟩. ⟨ensl-00351712⟩

Export

BibTeX TEI DC DCterms EndNote

Share

Metrics

Record views

201

Files downloads

383

Contact

Informations

CCSD