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Surface alignment, anchoring transitions, optical properties, and topological defects in the thermotropic nematic phase of organo-siloxane tetrapodes

Senyuk, B.; Kim, Y.-K.; Tortora, L.; Shin, S.-T.; Shiyanovskii, S. V.; Lavrentovich, O. D.; Kim, Y. -K.; Shin, S. -T.; Mehl, Georg; Kim, Young-Ki; Senyuk, Bohdan; Shin, Sung-Tae; Kohlmeier, Alexandra; Mehl, Georg H.; Lavrentovich, Oleg D.

Authors

B. Senyuk

Y.-K. Kim

L. Tortora

S.-T. Shin

S. V. Shiyanovskii

O. D. Lavrentovich

Y. -K. Kim

S. -T. Shin

Young-Ki Kim

Bohdan Senyuk

Sung-Tae Shin

Alexandra Kohlmeier

Oleg D. Lavrentovich

Abstract

We address the status of oxadiazole mesogens, C7 and C12, reported to show the biaxial nematic phase, by exploring material aspects (chemical stability, surface anchoring, optical and dielectric properties, topological defects) linked to the type of nematic order. We demonstrate that the isogyres splitting in conoscopic patterns of homeotropic state depends on sample thickness and is associated with variations of molecular tilt along the normal to substrates. We observe isolated topological point defects (boojums and hedgehogs), as well as nonsingular “escaped” disclinations pertinent only to the uniaxial nematic order. Our conclusion is that C7 and C12 feature only a uniaxial nematic phase and the apparent biaxiality is caused by surface effects.

Journal Article Type Article
Publication Date Jan 1, 2014
Journal Molecular crystals and liquid crystals
Print ISSN 1542-1406
Electronic ISSN 1563-5287
Publisher Taylor & Francis
Peer Reviewed Peer Reviewed
Volume 540
Issue 1
Pages 20-41
Institution Citation Kim, Y., Senyuk, B., Shin, S., Kohlmeier, A., Mehl, G. H., & Lavrentovich, O. D. (2014). Surface alignment, anchoring transitions, optical properties, and topological defects in the thermotropic nematic phase of organo-siloxane tetrapodes. Molecular crystals and liquid crystals, 540(1), 20-41. https://doi.org/10.1039/C3SM52249K
DOI https://doi.org/10.1039/C3SM52249K
Keywords Thermotropic nematic phase
Publisher URL http://www.tandfonline.com/doi/abs/10.1080/15421406.2011.568324
Copyright Statement ©2015 University of Hull
Additional Information This is an author's accepted manuscript of an article published in Molecular crystals and liquid crystals, 2011, v.540 issue 1.

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