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Oligomeric odd-even effect in liquid crystals

Saha, Rony; Babakhanova, Greta; Parsouzi, Zeinab; Rajabi, Mojtaba; Gyawali, Prabesh; Welch, Chris; Mehl, Georg H; Gleeson, Jim T.; Lavrentovich, Oleg D.; Sprunt, Samuel; Jakli, Antal

Authors

Rony Saha

Greta Babakhanova

Zeinab Parsouzi

Mojtaba Rajabi

Prabesh Gyawali

Chris Welch

Jim T. Gleeson

Oleg D. Lavrentovich

Samuel Sprunt

Antal Jakli



Abstract

Odd-even effects, oscillations in properties of materials comprised of an odd or even number of connected repeating units, are well-known phenomena in materials science. In organic materials, they are usually associated with the number of methylene groups in aliphatic chains. In this work, we unveil multiple signatures of a new odd-even effect in liquid crystals that occurs at the larger scale of molecular moieties that by themselves express liquid crystalline behavior. We demonstrate that oligomeric liquid crystals, with n=1-4 number of rigid mesogenic segments connected by flexible aliphatic chains with an odd number of methylene groups, produce an odd-even effect in optical anisotropy and the bend elastic constant of the liquid crystal oligomer. This effect is different from the usual odd-even effects with respect to the parity of carbon atoms in an aliphatic chain and can be understood in term of the average molecular shape and the associations between n-mers based on the packing of these shapes. We also show that, in spite of the fact that there is no long-range electron density modulation, careful analysis of synchrotron SAXS results can provide important information about the molecular associations in the N and NTB phases that other techniques cannot access. This novel odd-even effect opens up a new mode to optimize phase and optical behavior.

Journal Article Type Article
Publication Date Jun 13, 2019
Journal Materials Horizons
Print ISSN 2051-6347
Electronic ISSN 2051-6355
Peer Reviewed Peer Reviewed
Institution Citation Saha, R., Babakhanova, G., Parsouzi, Z., Rajabi, M., Gyawali, P., Welch, C., …Jakli, A. (2019). Oligomeric odd-even effect in liquid crystals. Materials Horizons, https://doi.org/10.1039/c9mh00428a
DOI https://doi.org/10.1039/c9mh00428a
Publisher URL https://pubs.rsc.org/en/Content/ArticleLanding/2019/MH/C9MH00428A