On the Miscibility of Nematic Liquid Crystals with Ionic Liquids and Joint Reaction for High Helical Twisting Power Product(s).

Maciej Czajkowski,Łukasz Duda,Bartłomiej Potaniec,Joanna Feder-Kubis,Joanna Cybińska

doi:10.3390/ma15010157

Abstract

Mixtures of nematic liquid crystals (LCs) with chiral ionic liquids (CILs) may find application as active materials for electrically driven broadband mirrors. Five nematic liquid crystal hosts were mixed with twenty three ionic liquids, including chiral ones, and studied in terms of their miscibility within the nematic phase. Phase diagrams of the mixtures with CILs which exhibited twisted nematic phase were determined. Miscibility, at levels between 2 and 5 wt%, was found in six mixtures with cyanobiphenyl-based liquid crystal host—E7. On the other hand, the highest changes in the isotropization temperature was found in the mixtures with isothiocyanate-based liquid crystal host—1825. Occurrence of chemical reactions was found. A novel chiral binaphtyl-based organic salt [N11116][BNDP] was synthesized and, in reaction to the 1825 host, resulted in high helical twisting power product(s). Selectivity of the reaction with the isothiocyanate-based liquid crystal was found.

Highlights

Induced broadening of the reflection band was presented in liquid crystal (LC) mixtures with chiral ionic liquids (CILs) [1,2]
ILs was doped into each of the LCs at the xIL in a range of 4.4–5.4%
The mixtures were characterized in terms of: (a) presence of a separate phase of the IL dopant; (b) shift in the isotropization temperature of the nematic phase of LC host (∆TNI ) of the nematic LC host; (c) presence of the twisted nematic phase

Summary

Introduction

Induced broadening of the reflection band was presented in liquid crystal (LC) mixtures with chiral ionic liquids (CILs) [1,2]. A miscibility of CILs with LCs within the nematic phase, besides sufficiently high helical twisting power (HTP) of the chiral dopant, seems to be the most crucial parameter for these applications. Such mixtures have already been studied in the literature [1,2,7,8,9,10,11,12], mainly with respect to their electrically induced effects. These examples should be treated as exceptions to the rule because lamellar smectic or columnar phases are preferred in most ionic liquid crystals [20], which, in turn, are not likely to mix with nematic LCs [21]

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Conclusion