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Crystals 2017, 7(12), 358;

Persistence of Smectic-A Oily Streaks into the Nematic Phase by UV Irradiation of Reactive Mesogens

LR99ES16 Laboratoire Physique de la Matière Molle et de la Modélisation Électromagnétique, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis, Tunisia
Institut des Nano-Sciences de Paris (INSP), CNRS UMR 7588, UPMC Univ Paris 06, Sorbonne Université, F75005 Paris, France
Department of Physics, Case Western Reserve University, Cleveland, OH 44106, USA
Author to whom correspondence should be addressed.
Academic Editor: Helmut Cölfen
Received: 27 September 2017 / Revised: 26 November 2017 / Accepted: 30 November 2017 / Published: 3 December 2017
(This article belongs to the Section Liquid Crystals)
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Thin smectic liquid crystal films with competing boundary conditions (planar and homeotropic at opposing surfaces) form well-known striated structures known as “oily streaks”, which are a series of hemicylindrical caps that run perpendicular to the easy axis of the planar substrate. The streaks vanish on heating into the nematic phase, where the film becomes uniform and exhibits hybrid alignment. On adding sufficient reactive mesogen and polymerizing, the oily streak texture is maintained on heating through the entire nematic phase until reaching the bulk isotropic phase, above which the texture vanishes. Depending on the liquid crystal thickness, the oily streak structure may be retrieved after cooling, which demonstrates the strong impact of the polymer backbone on the liquid crystal texture. Polarizing optical, atomic force, and scanning electron microscopy data are presented. View Full-Text
Keywords: liquid crystal; topological defect; oily streak; reactive mesogen liquid crystal; topological defect; oily streak; reactive mesogen

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Gharbi, I.; Missaoui, A.; Demaille, D.; Lacaze, E.; Rosenblatt, C. Persistence of Smectic-A Oily Streaks into the Nematic Phase by UV Irradiation of Reactive Mesogens. Crystals 2017, 7, 358.

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