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

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.

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, 6(9), 1905-1912. https://doi.org/10.1039/c9mh00428a

• Journal Article Type: Article
• Acceptance Date: Jun 13, 2019
• Online Publication Date: Jun 13, 2019
• Publication Date: Nov 1, 2019
• Deposit Date: Jun 13, 2019
• Publicly Available Date: Jun 14, 2020
• Journal: Materials Horizons
• Print ISSN: 2051-6347
• Electronic ISSN: 2051-6355
• Peer Reviewed: Peer Reviewed
• Volume: 6
• Issue: 9
• Pages: 1905-1912
• DOI: https://doi.org/10.1039/c9mh00428a
• Public URL: https://hull-repository.worktribe.com/output/1988429
• Publisher URL: https://pubs.rsc.org/en/Content/ArticleLanding/2019/MH/C9MH00428A