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Induced smectic phase in binary mixture of twist-bend nematogens

Knežević, Anamarija; Dokli, Irena; Sapunar, Marin; Šegota, Suzana; Baumeister, Ute; Lesac, Andreja (2018) Induced smectic phase in binary mixture of twist-bend nematogens. Beilstein Journal of Nanotechnology, 9 . pp. 1297-1307. ISSN 2190-4286

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The investigation of liquid crystal (LC) mixtures is of great interest in tailoring material properties for specific applications. The recent discovery of the twist-bend nematic phase (NTB) has sparked great interest in the scientific community, not only from a fundamental viewpoint, but also due to its potential for innovative applications. Here we report on the unexpected phase behaviour of a binary mixture of twist-bend nematogens. A binary phase diagram for mixtures of imino- linked cyanobiphenyl (CBI) dimer and imino- linked benzoyloxy-benzylidene (BB) dimer shows two distinct domains. While mixtures containing less than 35 mol % of BB possess a wide temperature range twist-bend nematic phase, the mixtures containing 55–80 mol % of BB exhibit a smectic phase despite that both pure compounds display a Iso–N–NTB–Cr phase sequence. The phase diagram shows that the addition of BB of up to 30 mol % significantly extends the temperature range of the NTB phase, maintaining the temperature range of the nematic phase. The periodicity, obtained by atomic force microscopy (AFM) imaging, is in the range of 6– 7 nm. The induction of the smectic phase in the mixtures containing 55–80 mol % of BB was confirmed using polarising optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction. The origin of the intercalated smectic phase was unravelled by combined spectroscopic and computational methods and can be traced to conformational disorder of the terminal chains. These results show the importance of understanding the phase behaviour of binary mixtures, not only in targeting a wide temperature range but also in controlling the self-organizing processes.

Item Type: Article
Additional Information: The authors thank the Croatian Science Foundation (grant ref. IP-2014-09-1525) for financial support. We are also grateful to Dr. Danijela Vojta (Ruder Boskovic Institute, Zagreb) for helpful discussions concerning IR measurements.
Uncontrolled Keywords: binary mixture; liquid crystals; smectic phase induction; temperature-dependent FT-IR; twist-bend nematogen
Subjects: NATURAL SCIENCES > Chemistry
NATURAL SCIENCES > Chemistry > Organic Chemistry
Divisions: Division of Organic Chemistry and Biochemistry
Division of Physical Chemistry
Project titleProject leaderProject codeProject type
Kiralnost od akiralnih tekućih kristala-CALCAndreja LesacIP-2014-09-1525HRZZ
Depositing User: Marin Sapunar
Date Deposited: 29 Nov 2019 13:03
DOI: 10.3762/bjnano.9.122

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